Research Article
J Pediatri Endocrinol. 2022; 7(1): 1049.
Racism May Weaken the Brain-Behavior Association among African American Children: The Case of Amygdala Volume-Emotion Regulation Link
Assari S1,2,3*, Najand B1 and Mays VM4,5,6
1Marginalization Related Diminished Returns Research Center, Charles R. Drew University of Medicine and Science, Los Angeles, CA, USA
2Department of Family Medicine, Charles R. Drew University of Medicine and Science, Los Angeles, CA, USA
3Department of Urban Public Health, Charles R. Drew University of Medicine and Science, Los Angeles, CA, USA
4BRITE Center for Science, Research & Policy, UCLA, Los Angeles, CA, USA
5Department of Health Policy, Fielding School of Public Health, UCLA, Los Angeles, CA, USA
6Department of Psychology, UCLA, Los Angeles, CA, USA
*Corresponding author: Shervin Assari, Marginalization Related Diminished Returns Research Center, Charles R. Drew University of Medicine and Science, Los Angeles, CA, USA
Received: January 10, 2022; Accepted: February 28, 2022; Published: March 07, 2022
Abstract
Introduction: The amygdala has a central core role in regulating emotions. However, less is known about the racial/ethnic variation in the relevance of amygdala volume for emotion regulation of US children. According to the Minorities’ Diminished Returns (MDRs) phenomenon, due to racism, segregation, and social stratification (rather than innate differences due to genetics), some of the individual-level individual social determinants, could lose some of their relevance for African American (in comparison to White) children.
Purpose: Conceptualizing race as a social factor that reflects structural racism and discrimination and building on the MDRs framework, we explored racial variation in the magnitude of the association between amygdala volume and emotion regulation/impulsivity of US children.
Methods: For this cross-sectional study, we used baseline data which included behavioral, social, and structural magnetic resonance imaging (MRI) data of 6030 US children ages 9-10. Data came from the Adolescent Brain Cognitive Development (ABCD) study. The primary outcomes were positive and negative urgency. These were measured using Urgency, Premeditation (lack of), Perseverance (lack of), Sensation Seeking, Positive Urgency, and Impulsive Behavior Scale (UPPS-SS) UPPS-SS. The independent variables were right and left amygdala volume. The covariates were age, sex, parental education, household income, parental marital status, neighborhood socioeconomic status, and ethnicity. Race was the moderator.
Results: Children with larger amygdala volumes had lower positive and negative urgency. The correlations between amygdala volume and positive and negative urgency were modified by race. For White children, children had better emotion regulation when they had a large amygdala. For African American children, positive and negative urgency did not show an association with amygdala size.
Conclusions: The results can be explained by the Minorities’ Diminished Returns (MDRs) hypothesis. In line with MDRs and as a result of structural and interpersonal inequalities, such as school segregation, the amygdala-emotion regulation seen for White children does not replicate for African American children. For White children, however, in the absence of higher-level social determinants, amygdala size correlates with emotion regulation. The brainbehavior link is weaker for African American children whose lives are less predictable and affected by experiences of racial discrimination. Unequal effects of equal resources across racial groups are due to racism and discrimination, not biological innate differences such as genetics.
Keywords: Amygdala; Limbic System; Children; MRI; Population groups; Emotion Regulation; Impulse Control; Inhibitory Control
Introduction
The right and left amygdala, almond-like structures [1], located deep in the brain’s medial temporal lobe of each hemisphere, are core elements of the limbic system and play a major role in emotion processing and regulation [2-9]. For humans and animals, the right and left amygdala modulate all reactions to emotionally charged events and sensory input [2]. The role of the amygdala in regulating human emotions and behaviors is well-described [10-13]. This subcortical brain structure processes emotionally charged, rewarding, and or threatening environmental inputs and stimuli [14] and has a major role in emotions [1]. Although the amygdala is best known for its role in processing fear and threat, it also has a role in emotion regulation, inhibitory control, and decision making [15]. While changes of the amygdala are best known in anxiety disorders such as general anxiety disorder (GAD), post-traumatic stress disorder (PTSD) [4-6,16], phobias and panic disorder (PD) [17], altered amygdala function and size is shown for other disorders and problem such as autism, schizophrenia [18,19], aggression [20,21] and depression [22].
The amygdala size- emotion regulation is well described in the neuroscience literature [23]. As a result, youth and adults with a smaller amygdala are at an increased risk of mood disorders [24] such as bipolar disorder [25] and depression [22,26]. In most disorders mentioned above, the amygdala is small but hyperactive [24,27]. It is, however, unknown if behavioral correlation of amygdala size differs across population sub-groups, particularly those racialized as White and African American [28].
Race, which can closely overlap with socioeconomic status (SES) and chronic stress, can serve as a proxy of exposure to racism and other environmental factors that may impact various brain structures including the amygdala [29-32]. Race impacts amygdala and other brain structures, because racial/ethnic minority populations are chronically exposed to various forms of discrimination, stress, and economic disadvantages [33]. Thus; some of the race effects on the brain can be a function of the experiences associated with SES, particularly at the lower end especially in the case of poverty like experiences [33]. However, the SES effects on brain may also vary by race. Some studies have shown that SES effects on shaping some brain structures may be more robust for low SES children [33]. Due to racism, discrimination, and segregation, however, racial minority groups may not show the effects of SES on brain [34]. This is recently described as racism-related diminished returns of SES on children’s brain development [35,36].
Minorities’ Diminished Returns (MDRs) have been shown?? To have weaker SES effects for African Americans than White individuals. These MDRs emerge because high SES African American families have lower household income and wealth and experience higher levels of stress and discrimination [37-41]. As a result of residential segregation, moderate to high SES African American children can remain with high-risk peers [42] and in high-risk schools [43] and neighborhoods [44]. Similarly, moderate to high SES African American children still experience high levels of chronic stress [44-46], which have been shown to hinder their healthy brain development [8,47-49]. Similar MDRs are shown for the effects of SES on trauma [46], ADHD [50], suicide [51], depression [52], anxiety [53], aggression [54], tobacco use [54-56], impulsivity [57], school bonding [58], school performance [59], and inhibitory control [60]. All these SES effects are stronger in White than African American youth. These African American-White differences in the SES effects (i.e., MDRs) are frequently replicated [41,61-63], suggesting that weakened effect of SES in African American than White children is a robust phenomenon [61]. In this view, family-level SES have smaller than expected effects on shaping African American children’s brain development [50,63-68]. That means it is related to the social structural -level barriers (e.g., segregation) and interpersonal stressors (e.g., discrimination) that SES resources lose some of their effects for African Americans when compared to Whites [61]. For example, due to experiences like labor market discrimination, segregation, and racism, experiences of high-SES and low-SES African American families are more similar [61] than among high-SES and low-SES White families [37]. This is partly because SES can be more protective for populations which do not face chronic forms of race-based discrimination (e.g., American Whites) [38,69].
In the Adolescent Brain Cognitive Development (ABCD) study [70-73], family SES increased the amygdala size for White children but not African American children [34]. Similar patterns were observed for the thalamus [74], hippocampus [75], cerebral cortex [76,77], and cerebellum [78]. In another paper, SES showed stronger effects on brain structure and function in White people than African American people [79].
MDRs, however, are not limited to SES. Not only economic but also non-economic resources and assets lose some of their beneficial or protective effects in African Americans than Whites [63,80,81]. For example, age, emotion regulation, self-efficacy, and coping show larger positive health consequences for Whites than African Americans [82- 89]. In the same manner that SES indicators have weaker effects on positive health outcomes for African Americans than Whites. As a function of racism and discrimination, brain mechanisms and how brain structures function under these conditions may have weaker effects on behavioral and physical health outcomes for African Americans than White communities [38,90].
Aims
Employing data from the ABCD study and the MDRs framework, we used the behavioral [54] and brain imaging data [34] to investigate the differential effect of amygdala size on positive/negative urgency of 9-10 years old American children. Our first hypothesis was an inverse association between amygdala size and positive/negative urgency of the children. Our second hypothesis was a weaker association between amygdala size and positive/negative urgency as a proxy of emotion regulation and impulsivity for African American than White children. In other words, we expect high levels of positive/ negative urgency for African American children regardless of the child’s amygdala size. For White children, however, our prediction is an inverse association between amygdala size and positive/negative urgency (as a proxy of emotion regulation and impulsivity).
Methods
Design and settings
This was a secondary analysis of wave 1 of the Adolescent Brain Cognitive Development (ABCD) study [70-73]. The ABCD is national existing data of brain imaging and child development. The ABCD data was borrowed from the NDA website. The ABCD is a landmark brain development study of United States youth. Detailed information on the ABCD methods, sampling, sample, measures, and imaging techniques are available here [70-73,91,92].
Participants and sampling
The ABCD participants were 9-10 children, who were between ages 9 and 11 years. Children in the ABCD study were recruited from multiple cities across multiple states. Overall, participants were enrolled from 21 different sites. The primary source of recruitment for the ABCD sample was US school systems. The sampling protocol of the ABCD study is described in detail here [70]. In the specific analysis, our sample was composed of a total number of 6030 9-10-year-old participants who were either White or African American. Our analysis’s eligibility included valid data on race, ethnicity, demographics, parental education, parental marital status, amygdala volume, and positive and negative urgency.
Study variables
Amygdala volume: The independent variables were the right and the left amygdala volume (mm3), measured by structural MRI at rest, as described here [93].
Moderator
Race: Race was self-identified by the parent. Race was a dichotomous variable: African American and White (reference category).
Outcomes: Outcomes were positive and negative urgency. These were measured using the Urgency, Premeditation (lack of), Perseverance (lack of), Sensation Seeking, Positive Urgency, Impulsive Behavior Scale (UPPS-SS) UPPS-SS. Positive and negative urgency are correlated constructs that reflect two inter-related aspects of impulsivity. Positive urgency is the inability to wait and postpone reward. Negative urgency is the inability to tolerate negative input. In this study, positive urgency was treated as a continuous measure, with a higher score indicating higher positive urgency traits (higher impulsivity). The UPPS-SS is a valid and reliable measure [94-100]. These constructs have shown reliability and validity in past research [101-103].
Age, sex, ethnicity, household income, parental education, neighborhood SES, and parental marital status were the confounding variables. Ethnicity was measured by the self-identification of the parents. Ethnicity was a dichotomous variable and coded 1 for Latino and 0 for non-Latino (reference category) families. Parents reported children’s age which was calculated as months passed since birth. Sex of the child was a dichotomous variable that was coded 0 for males and 1 for females. Parental educational attainment was an ordinal variable: less than high school (reference category), high school, college, graduate + school. Parental marital status was also a dichotomous variable, self-reported by the parent interviewed, and coded 1 vs. 0 for married and unmarried families respectively. Parental education was a continuous measure reflecting years of schooling. Household income was a continuous measure ranging from 1 to 10, with a higher score indicating higher SES. We also used Area Deprivation Index (Neighborhood disorder) [104] as the measure of social context.
Data analysis
We used SS 25.0 for data analysis. The primary outcomes were positive and negative urgency. The independent variables were right and left amygdala volume. Covariates were age, sex, parental marital status, parental education, Area Deprivation Index (Neighborhood disorder) [104], and ethnicity. Model 1 tested the additive effects of amygdala size and race, with the same covariates, without interaction terms. Model 2 tested the interaction between amygdala size and race with all covariates. We ran identical models for the right and left amygdala and positive and negative urgency. Before running our models, we checked a wide range of assumptions, including normal distribution of our outcomes, lack of collinearity between predictors and covariates, and the distribution of errors for our models.
Ethical aspect
Our secondary analysis was found by the Charles R Drew University of Medicine and Science (CDU) Institutional Review Board (IRB) to be exempt from a full IRB review. However, the original ABCD study underwent an Institutional Review Board (IRB) in several institutions, including but not limited to the University of California, San Diego (UCSD). The IRB in multiple institutions approved the ABCD study protocol, and all of the children provided assent, and the parents signed consent.
Results
Sample descriptive data
Table 1 shows descriptive data overall. This study included 6030 children who were 9-10 year of age. From this number, 75.6% were White, and 24.4% were African American. Table 1 also compared study variables by race. African American and White children did not differ in age or sex, but they differed in Hispanic ethnicity, positive and negative urgency, SES, and right and left amygdala volume (size).
All
African American
White
n
%
n
%
n
%
Race
White
4558
75.6
-
-
4558
100
AA
1472
24.4
1472
100
-
-
Ethnicity
Non
5044
83.6
1346
91.4
3698
81.1
Latino*
986
16.4
126
8.6
860
18.9
Sex
Female
2633
43.7
684
46.5
1949
42.8
Male
3397
56.3
788
53.5
2609
57.2
Puberty*
Pre
1634
27.1
280
19
1354
29.7
None
4396
72.9
1192
81
3204
70.3
Married Family*
No
1946
32.3
974
66.2
972
21.3
Yes
4084
67.7
498
33.8
3586
78.7
Mean
SD
Mean
SD
Mean
SD
Age
9.4951
0.50843
9.486
0.5137
9.498
0.50674
Residential history derived - Area Deprivation Index
(based on Kind et al., Annals of Internal Medicine, 2014)*93.56
24.408
104.86
21.825
89.9
24.078
Parental Education*
16.7706
2.56602
15.3988
2.57596
17.2137
2.40108
Financial Difficulty*
0.0687
0.16051
0.1446
0.21859
0.0442
0.1273
Amygdala Volume (Right)/1000*
1.6179
0.2266
1.5499
0.21269
1.6399
0.22661
Amygdala Volume (Left)/1000*
1.5757
0.23124
1.4955
0.21234
1.6016
0.23116
Positive Urgency*
7.98
2.944
8.57
3.207
7.78
2.828
Negative Urgency*
8.52
2.645
8.81
2.859
8.42
2.565
*p<0.001 for comparison of African American and White children.
Table 1: Descriptive statistics in the pooled sample by race.
Regressions
Positive urgency: As shown by Table 2, the right and left amygdala size affected positive urgency when all confounders were controlled. However, the protective effect of children’s right amygdala size on positive urgency was smaller in African Americans than in White children.
Model 1
Model 2
b
SE
Beta
95%CI
p
b
SE
Beta
95%CI
p
Right
Race (AA)
0.336
0.102
0.049
0.137
0.536
0.001
-1.241
0.64
-0.181
-2.496
0.014
0.053
Ethnicity (Hispanic)
-0.081
0.105
-0.01
-0.288
0.125
0.439
-0.089
0.105
-0.011
-0.295
0.118
0.399
Age (Yr)
-0.148
0.074
-0.025
-0.292
-0.003
0.046
-0.145
0.074
-0.025
-0.29
-0.001
0.049
Male
0.58
0.08
0.098
0.423
0.736
0
0.579
0.08
0.098
0.423
0.735
0
Puberty
0.349
0.085
0.053
0.182
0.516
0
0.351
0.085
0.053
0.185
0.518
0
Married
-0.185
0.092
-0.029
-0.365
-0.005
0.044
-0.189
0.092
-0.03
-0.37
-0.009
0.039
Area Deprivation Index (Kind 2014)
0.004
0.002
0.029
0
0.007
0.032
0.004
0.002
0.03
0
0.007
0.029
Parental Education
-0.078
0.017
-0.068
-0.111
-0.045
0
-0.077
0.017
-0.067
-0.11
-0.044
0
Financial Difficulty
0.996
0.251
0.054
0.505
1.487
0
1.004
0.251
0.055
0.513
1.495
0
Right Amygdala Volume/1000
-0.467
0.177
-0.036
-0.815
-0.12
0.008
-0.689
0.198
-0.053
-1.078
-0.3
0.001
Right Amygdala Volume/1000 x Race (AA)
1.003
0.402
0.23
0.215
1.79
0.013
Left
Race (AA)
0.323
0.102
0.047
0.123
0.523
0.002
-0.288
0.62
-0.042
-1.503
0.927
0.642
Ethnicity (Hispanic)
-0.091
0.105
-0.011
-0.297
0.116
0.389
-0.096
0.105
-0.012
-0.302
0.111
0.364
Age (Yr)
-0.14
0.074
-0.024
-0.285
0.004
0.057
-0.141
0.074
-0.024
-0.286
0.004
0.057
Male
0.589
0.079
0.099
0.433
0.745
0
0.589
0.079
0.099
0.433
0.745
0
Puberty
0.35
0.085
0.053
0.184
0.517
0
0.351
0.085
0.053
0.184
0.518
0
Married
-0.184
0.092
-0.029
-0.364
-0.004
0.046
-0.186
0.092
-0.03
-0.366
-0.006
0.043
Area Deprivation Index (Kind 2014)
0.003
0.002
0.029
0
0.007
0.036
0.003
0.002
0.029
0
0.007
0.034
Parental Education
-0.078
0.017
-0.068
-0.111
-0.045
0
-0.078
0.017
-0.068
-0.111
-0.045
0
Financial Difficulty
0.988
0.251
0.054
0.497
1.479
0
0.995
0.251
0.054
0.504
1.487
0
Right Amygdala Volume/1000
-0.54
0.174
-0.042
-0.882
-0.198
0.002
-0.625
0.194
-0.049
-1.006
-0.244
0.001
Right Amygdala Volume/1000 x Race (AA)
0.401
0.401
0.089
-0.385
1.187
0.317
Table 2: Association between amygdala volume and positive urgency.
Negative urgency: As shown by Table 3, the right and left amygdala size affected negative urgency when all confounders were controlled. However, the protective effects of children’s right and left amygdala size on negative urgency were smaller in African American children than in White children.
Model 1
Model 2
b
SE
Beta
95%CI
p
b
SE
Beta
95%CI
P
Right
Race (AA)
0.164
0.092
0.027
-0.017
0.344
0.076
-1.731
0.579
-0.281
-2.866
-0.597
0.003
Ethnicity (Hispanic)
-0.32
0.095
-0.045
-0.506
-0.133
0.001
-0.328
0.095
-0.046
-0.515
-0.142
0.001
Age (Yr)
-0.077
0.067
-0.015
-0.207
0.054
0.252
-0.074
0.067
-0.014
-0.205
0.057
0.268
Male
0.601
0.072
0.113
0.46
0.742
<0.001
0.6
0.072
0.113
0.459
0.741
<0.001
Puberty
0.466
0.077
0.078
0.316
0.617
<0.001
0.469
0.077
0.079
0.318
0.62
<0.001
Married
-0.028
0.083
-0.005
-0.191
0.135
0.735
-0.033
0.083
-0.006
-0.196
0.129
0.687
Area Deprivation Index (Kind 2014)
-0.002
0.001
-0.018
-0.005
0.001
0.188
-0.002
0.001
-0.017
-0.005
0.001
0.202
Parental Education
-0.049
0.015
-0.048
-0.079
-0.019
0.001
-0.049
0.015
-0.047
-0.079
-0.019
0.001
Financial Difficulty
0.595
0.227
0.036
0.151
1.039
0.009
0.605
0.226
0.037
0.161
1.049
0.008
Right Amygdala Volume/1000
-0.321
0.16
-0.028
-0.635
-0.007
0.045
-0.587
0.179
-0.05
-0.939
-0.236
0.001
Right Amygdala Volume/1000 x Race (AA)
1.204
0.363
0.307
0.493
1.916
0.001
Left
Race (AA)
0.159
0.092
0.026
-0.023
0.34
0.086
-1.042
0.56
-0.169
-2.14
0.056
0.063
Ethnicity (Hispanic)
-0.324
0.095
-0.045
-0.511
-0.137
0.001
-0.333
0.095
-0.047
-0.52
-0.146
<0.001
Age (Yr)
-0.073
0.067
-0.014
-0.204
0.058
0.274
-0.074
0.067
-0.014
-0.205
0.057
0.271
Male
0.599
0.072
0.112
0.459
0.74
<0.001
0.599
0.072
0.112
0.458
0.74
<0.001
Puberty
0.467
0.077
0.079
0.316
0.618
<0.001
0.468
0.077
0.079
0.318
0.619
<0.001
Married
-0.028
0.083
-0.005
-0.191
0.135
0.737
-0.032
0.083
-0.006
-0.195
0.131
0.699
Area Deprivation Index (Kind 2014)
-0.002
0.001
-0.018
-0.005
0.001
0.179
-0.002
0.001
-0.018
-0.005
0.001
0.192
Parental Education
-0.05
0.015
-0.048
-0.079
-0.02
0.001
-0.049
0.015
-0.048
-0.079
-0.019
0.001
Financial Difficulty
0.593
0.227
0.036
0.149
1.037
0.009
0.608
0.227
0.037
0.163
1.052
0.007
Right Amygdala Volume/1000
-0.316
0.158
-0.028
-0.625
-0.007
0.045
-0.484
0.176
-0.042
-0.829
-0.14
0.006
Right Amygdala Volume/1000 x Race (AA)
0.788
0.363
0.194
0.077
1.498
0.03
Table 3: Association between amygdala volume and negative urgency.
Discussion
Overall, we found inverse associations between the right and left amygdala size and positive and negative urgency as a proxy of impulsivity of Black and White US children. However, the links between amygdala volume and impulsivity were weaker for African American children than for White children. This was shown by statistical interactions between children’s amygdala size and race on indicators of impulsivity. This provides an example of African American children’s relative disadvantage compared to White children in the behavioral returns of their amygdala size (brainbehavior link).
Our observed results (statistical interactions) are in line with the Minorities’ Diminished Returns (MDRs) framework. As explained by the MDRs framework, due to structural inequalities, segregation, and even interpersonal discrimination, an increase in amygdala size would not result in the same level of favorable behavior for African American children compared to White children. This is also described as racism-related unequal effects of equal resources across racial groups [105,106].
Larger amygdala size in children was associated with less impulsivity (urgency). However, this gain was larger for White children than for African American children. The brain-behavior link is well established [101-103,107,108]. Brain measures including amygdala volume correlate with emotional, behavioral, and cognitive function [109-111]. However, the environment – brain-behavior link may vary across social groups [112].
Our second finding is that change in amygdala size is linked to a smaller improvement in expected behaviors for African Americans than Whites. This is well described as MDRs [105,106]. In the Adolescent Brain Cognitive Development (ABCD) [51,60,64,113], Add Health [114], Fragile Families and Child Wellbeing Study (FFCWS) [50,57,58,115-118], Monitoring the Future (MTF) [59], National Survey of American Life (NSAL) [52], Flint Adolescents Study (FAS) [53], and Family and Community Health Study (FACHS) [119,120] data sets, age, SES indicators, and other resources and assets generate fewer developmental outcomes for African American and other ethnic minorities than for Whites. For example, high SES shows a larger effect on depression [52], anxiety [53], aggression [54], tobacco use [56], school attachment [58], school performance [59], attention deficit hyperactivity disorder (ADHD) [50], impulsivity [57], inhibitory control [121], stress [46,115], obesity [118], and physical health [54] for White children than for African American children. This is in part because individual-level resources and assets do not reflect the very same t phenomenon across contexts. The same resource can do much less for marginalized group in highly segregated poverty-driven urban areas than highly-resourced suburban context.
The most closely relevant MDRs research findings is a recent study that showed a diminished effect of children’s amygdala size on teachers’ reported behavioral problems of African American children. The paper used the ABCD study and showed that the relevance of the amygdala for teacher reports of the behavioral problem was diminished for African American than White children [122]. Another study showed diminished effects of age on inhibitory control. Other papers reported weaker effects of positive and negative urgency on suicidality [123] and obesity [123] for African American children than for White children.
To give other research support of the role of MDRs, we found a higher prevalence of depression in high SES African American children and adults [52,119,120,124-126]. In Flint, Michigan, White children from married families were protected against future symptoms of anxiety; however, this was not the case for African American children, whose family structure did not protect against subsequent anxiety symptoms [53]. In the Fragile Families and Child Wellbeing Study (FFCWS), which followed a sample of African American and White children from birth to age 15, family SES at birth better improved mental and physical health of White than African American children at age 15 [57,118,127]. White but not Black children from high SES families were protected against ADHD [50]. In the Population Assessment of Tobacco and Health (PATH) data, high-SES African American children remain at risk of tobacco use, while high SES White children were protected against tobacco use [56]. In the Monitoring the Future (MTF) data, high- SES White children earned the highest grade point average (GPA), while for African American children, GPA remained low in high SES people [59]. Finally, high-SES White children were protected against aggression, obesity, tobacco use, and chronic disease in the PATH data. However, African American children remained at risk of these conditions across all SES levels [54].
The MDRs are not specific only to African Americans. Diminished returns of SES indicators and other resources and assets [106] are seen for Latino [54], Asian American [128], Native American [129] LGBT [130,131], immigrant [132,133], and even marginalized White [114] people. Thus, MDRs findings are due to the mechanisms that occur in marginalization and racism [114]. Based on this model, any marginalized social identities would be associated with diminished effects of resources and assets for marginalized people. Any social status deviation from “US-born non-Latino heterosexual Whiteness” comes with a detrimental penalty in the US, which can be documented as lower returns of resources and assets at the individual and population based levels.
The observed MDRs can be attributed to unequal access to opportunity structure, different neighborhood effects, and daily experiences that collectively in the US are associated with racism and social structural diminished opportunities. The MDRs framework argues that due to structural racism, social stratification, and contextual inequalities, individual-level resources and assets show diminished returns for African American and other marginalized populations compared to Whites [105,134]. Individual-level and even family-level resources and assets, either SES or brain structure, show smaller effects for African American children than White children, because a wide range of contextual and higherlevel barriers are in play and continually hinder African American communities. Discrimination is a daily chronic stressors experienced by African Americans across their life span from cradle to grave [135-138]. Compared to White families, African American families pay far more psychological and physiological taxes as costs in their upward social mobility [90]. Across all levels of resources and assets, African Americans, as a group, experience high levels of stress and discrimination [46,115], and live in high-risk schools, neighborhoods [44], and workplaces [43]. Across all SES levels, African American children are more likely to spend time with high-risk peers [43] and relatives [42]. In such context, variation in individual-level resources and assets may lose some of their behavioral or health effects [106,134]. African Americans, as a group, experience adversity, which show some risk outcomes, regardless of their individual-level resource, asset, resilience, or risk profile.
A few limitations can be discussed in this study. First, this study only investigated the correlation of amygdala volume, not other characteristics of the amygdala, such as resting-state function, task-based function, diffusivity, and functional connectivity. This study also only investigated the right and left amygdala, without studying other brain structures such as the thalamus, cerebral cortex, hippocampus, putamen, and nucleus accumbens.
Any results on the terms diminished, race, and brain development are prone to misinterpretation. As such, we need to make our position clear. We distance ourselves from any deterministic view to race and brain development. We do not suggest that one race is superior to the other race. We study brain structures and functions to document the mechanism of a negative frequent experience of racism in reducing the functional capacities of African Americans in their behavioral and physical health outcomes. This is an established observation outside the neuroscience field, and we are hoping to replicate the findings outside the neuroscience within this field. As such, similar to other domains such as mortality, chronic disease, and economic outcomes, the observed differences are shaped by social forces that hinder African American communities regardless of their variation in individuallevel determinants. Studying mechanisms of social inequalities at the brain level is a step forward. However, we acknowledge that some readers may mistakenly interpret our results as biological determinism. We distance ourselves from such biological views and deterministic genetic effect on IQ and cognition. Our findings in the area of brain should be interpreted and seen in conjunction with the MDRs for Latino [54], Asian American [128], Native American [129] LGBT [130,131], immigrant [132,133], and even marginalized White [114] that share one element: marginalization. No difference, that systematic at the population level, can be due to genes. Similarly, these findings are not due to culture or behavior of African Americans at an individual level. Attributing these findings to cultural differences unfortunately is concluded when we do not consider racism and similar historic forces that reduce opportunity at the population level.
This study went beyond describing MDRs of parental and family SES on youth and children outcomes. The next step is quantifying the existing MDRs and societal causes of the observed MDRs. Research may explore how social context limits the behavioral correlation of brain structures and which social or public policies can equalize the returns of resources across racial groups. More research is needed on the mechanisms by which residential and school segregation, stratification, and discrimination contribute to African American children being high risk at all levels of risk factors. There is also a need to study structural, social, and environmental processes that cause these MDRs in African American communities. In addition, we need to investigate economic, public, education, and social policies that help reduce the existing risk for children in African American families and their children.
Limitations
Despite contributing to the literature, there were a few methodological issues which were difficult to address. Thus; our interpretation of the findings should be with caution. First, the amygdala has been linked to emotional responses much more than to emotional regulation. Mechanistically, it makes more sense based on what we know while higher cortical areas (vMPFC, DLPFC) and hippocampus are much more “tightly” linked to regulation. Second, amygdala volume studies are all correlative and assuming directionality here has no grounds. This is a profound issue with this paper. For example, Amygdala volume could be the outcome of inhibitory inputs from cortical regions similarly to behavior etc. Finally, the difference in sample sizes between Black and White participants was a problem. This could affect the significance and the strength of findings and could explain all the differences in association (not causation) between Amygdala volume and SES.
Implications
Under racism, segregation, and stratification, the effects of brain structures such as the amygdala are weaker for African American than White children. This observation is in line with the MDRs in the SES effects. While large amygdala volume reduces impulsivity, this effect is weaker for African American children than for White children. Unequal effects of equal resources are a novel mechanism that may explain some inequalities by race and ethnicity. MDRs in African American communities reflect deep structural inequalities that not only shape access to resources and assets, but also limit how much they can generate outcomes for each group. As such, at the same level of resources, African American children do worse than White children. As a result, eliminating the racial gap is necessary but not enough to promote racial equity.
Conclusion
While larger amygdala size is associated with lower impulsivity for US children, this effect is weaker for African American children than for White children. We see MDRs for the effects of SES on the amygdala [34] and MDRs for the effects of the amygdala size on impulsivity. We argue that MDRs are relevant to the effects of environmental and social inputs on the brain as well as the effects of the brain on behavior. Our approach to eliminating health inequalities requires efforts beyond equalizing SES and resources. Due to existing racism and segregation, the links between SES resources, age, brain structures, and outcomes are weaker for African American children than for White children. A true solution to health inequalities should include strategies to reduce racism, stratification, and segregation in the US.
Declaration
Conflicts of Interest: The funders had no role in the design of the study, in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
Author contributions: S.A: Conceptualization, formal analysis, original draft preparation, and revision; V.M: review of methods, editing and revisions.
Acknowledgments: Data used in the preparation of this article were obtained from the Adolescent Brain Cognitive Development (ABCD) Study (https://abcdstudy.org), held in the NIMH Data Archive (NDA). This is a multisite; longitudinal study designed to recruit more than 10,000 children aged 9-10 years and follows them over 10 years into early adulthood. The ABCD Study is supported by the National Institutes of Health and additional federal partners under award numbers U01DA041022, U01DA041028, U01DA041048, U01DA041089, U01DA041106, U01DA041117, U01DA041120, U01DA041134, U01DA041148, U01DA041156, U01DA041174, U24DA041123, and U24DA041147. A full list of supporters is available at https://abcdstudy.org/nih-collaborators. A listing of participating sites and a complete listing of the study investigators can be found at https://abcdstudy.org/principal-investigators.html. ABCD consortium investigators designed and implemented the study and/or provided data but did not necessarily participate in analysis or writing of this report. This manuscript reflects the views of the authors and may not reflect the opinions or views of the NIH or ABCD consortium investigators. The ABCD data repository grows and changes over time. The ABCD data used in this report came from [NIMH Data Archive Digital Object Identifier (http://dx.doi. org/10.15154/1504041)]. Shervin Assari is supported by the National Institute of Minority Health and Health Disparities (NIMHD) of the National Institutes of Health under award number 5S21MD000103. The content is solely the responsibility of the authors and does not necessarily represent the official view of the NIMHD or NIH. Origins of this work were also supported by NIMHD 06923. This manuscript reflects the views of the authors and may not reflect the opinions or views of the NIH or ABCD consortium investigators.
References
- Brierley B, Shaw P, David A. The human amygdala: a systematic review and meta-analysis of volumetric magnetic resonance imaging. Brain Research Reviews. 2002; 39: 84-105.
- Gallagher M, Holland PC. The amygdala complex: multiple roles in associative learning and attention. Proceedings of the National Academy of Sciences. 1994; 91: 11771-11776.
- Liberzon I, Phan KL, Decker LR, Taylor SF. Extended amygdala and emotional salience: a PET activation study of positive and negative affect. Neuropsychopharmacology. 2003; 28: 726-733.
- Phan KL, Taylor SF, Welsh RC, et al. Activation of the medial prefrontal cortex and extended amygdala by individual ratings of emotional arousal: a fMRI study. Biol Psychiatry. 2003; 53: 211-215.
- Ahs F, Palmquist AM, Pissiota A, et al. Arousal modulation of memory and amygdala-parahippocampal connectivity: a PET-psychophysiology study in specific phobia. Psychophysiology. 2011; 48: 1463-1469.
- Sripada RK, King AP, Garfinkel SN, et al. Altered resting-state amygdala functional connectivity in men with posttraumatic stress disorder. J Psychiatry Neurosci. 2012; 37: 241-249.
- Sripada RK, Welsh RC, Marx CE, Liberzon I. The neurosteroids allopregnanolone and dehydroepiandrosterone modulate resting-state amygdala connectivity. Hum Brain Mapp. 2014; 35: 3249-3261.
- Javanbakht A, King AP, Evans GW, et al. Childhood Poverty Predicts Adult Amygdala and Frontal Activity and Connectivity in Response to Emotional Faces. Front Behav Neurosci. 2015; 9: 154.
- Evans GW, Swain JE, King AP, et al. Childhood Cumulative Risk Exposure and Adult Amygdala Volume and Function. J Neurosci Res. 2016; 94: 535- 543.
- Sarter M, Markowitsch HJ. Involvement of the amygdala in learning and memory: a critical review, with emphasis on anatomical relations. Behavioral neuroscience. 1985; 99: 342.
- Ressler KJ. Amygdala activity, fear, and anxiety: modulation by stress. Biol Psychiatry. 2010; 67: 1117-1119.
- Stevens JS, Kim YJ, Galatzer-Levy IR, et al. Amygdala Reactivity and Anterior Cingulate Habituation Predict Posttraumatic Stress Disorder Symptom Maintenance After Acute Civilian Trauma. Biol Psychiatry. 2017; 81: 1023-1029.
- Alexandra Kredlow M, Fenster RJ, Laurent ES, Ressler KJ, Phelps EA. Prefrontal cortex, amygdala, and threat processing: implications for PTSD. Neuropsychopharmacology. 2022; 47: 247-259.
- Tottenham N, Sheridan MA. A review of adversity, the amygdala and the hippocampus: a consideration of developmental timing. Frontiers in human neuroscience. 2010; 3: 68.
- Baas D, Aleman A, Kahn RS. Lateralization of amygdala activation: a systematic review of functional neuroimaging studies. Brain Research Reviews. 2004; 45: 96-103.
- King AP, Block SR, Sripada RK, et al. A Pilot Study of Mindfulness-Based Exposure Therapy in OEF/OIF Combat Veterans with PTSD: Altered Medial Frontal Cortex and Amygdala Responses in Social-Emotional Processing. Front Psychiatry. 2016; 7: 154.
- Shin LM, Rauch SL, Pitman RK. Amygdala, medial prefrontal cortex, and hippocampal function in PTSD. Annals of the New York Academy of Sciences. 2006; 1071: 67-79.
- Marsh AA, Finger EC, Mitchell DG, et al. Reduced amygdala response to fearful expressions in children and adolescents with callous-unemotional traits and disruptive behavior disorders. American Journal of Psychiatry. 2008; 165: 712-720.
- Machado CJ, Bachevalier J. Non-human primate models of childhood psychopathology: the promise and the limitations. Journal of Child Psychology and Psychiatry. 2003; 44: 64-87.
- Coccaro EF, McCloskey MS, Fitzgerald DA, Phan KL. Amygdala and orbitofrontal reactivity to social threat in individuals with impulsive aggression. Biological psychiatry. 2007; 62: 168-178.
- Pardini DA, Raine A, Erickson K, Loeber R. Lower amygdala volume in men is associated with childhood aggression, early psychopathic traits, and future violence. Biological psychiatry. 2014; 75: 73-80.
- Mervaala E, Föhr J, Könönen M, et al. Quantitative MRI of the hippocampus and amygdala in severe depression. Psychological medicine. 2000; 30: 117- 125.
- Hare TA, Tottenham N, Davidson MC, Glover GH, Casey B. Contributions of amygdala and striatal activity in emotion regulation. Biological psychiatry. 2005; 57: 624-632.
- Siegle GJ, Thompson W, Carter CS, Steinhauer SR, Thase ME. Increased amygdala and decreased dorsolateral prefrontal BOLD responses in unipolar depression: related and independent features. Biological psychiatry. 2007; 61: 198-209.
- Garrett A, Chang K. The role of the amygdala in bipolar disorder development. Development and psychopathology. 2008; 20: 1285-1296.
- Sheline YI, Gado MH, Price JL. Amygdala core nuclei volumes are decreased in recurrent major depression. Neuroreport. 1998; 9: 2023-2028.
- Monk CS, Klein RG, Telzer EH, et al. Amygdala and nucleus accumbens activation to emotional facial expressions in children and adolescents at risk for major depression. American Journal of Psychiatry. 2008; 165: 90-98.
- Ahmed S. Racialized bodies. In: Real bodies. Springer. 2002: 46-63.
- Brito NH, Fifer WP, Myers MM, Elliott AJ, Noble KG. Associations among family socioeconomic status, EEG power at birth, and cognitive skills during infancy. Dev Cogn Neurosci. 2016; 19: 144-151.
- Gianaros PJ, Hackman DA. Contributions of neuroscience to the study of socioeconomic health disparities. Psychosom Med. 2013; 75: 610-615.
- Hao Y, Farah MJ. The affective neuroscience of socioeconomic status: implications for mental health. BJPsych Bull. 2020: 1-6.
- Jenkins LM, Chiang JJ, Vause K, et al. Subcortical structural variations associated with low socioeconomic status in adolescents. Hum Brain Mapp. 2020; 41: 162-171.
- Noble KG, Houston SM, Brito NH, et al. Family income, parental education and brain structure in children and adolescents. Nat Neurosci. 2015; 18: 773-778.
- Assari S, Boyce S, Bazargan M. Subjective Socioeconomic Status and Children’s Amygdala Volume: Minorities’ Diminish Returns. NeuroSci. 2020; 1: 59-74.
- Assari S, Caldwell CH. Racism, Diminished Returns of Socioeconomic Resources, and Black Middle-Income Children’s Health Paradox. JAMA pediatrics. 2021.
- Assari S, Mincy R. Racism May Interrupt Age-related Brain Growth of African American Children in the United States. J Pediatr Child Health Care. 2021; 6.
- Assari S. Parental Education Better Helps White than Black Families Escape Poverty: National Survey of Children’s Health. Economies. 2018; 6: 30.
- Assari S. Understanding America: Unequal Economic Returns of Years of Schooling in Whites and Blacks. World J Educ Res. 2020; 7: 78-92.
- Assari S, Bazargan M. Unequal Associations between Educational Attainment and Occupational Stress across Racial and Ethnic Groups. International Journal of Environmental Research and Public Health. 2019; 16: 3539.
- Assari S. College Graduation and Wealth Accumulation: Blacks’ Diminished Returns. World J Educ Res. 2020; 7: 1-18.
- Assari S, Preiser B, Kelly M. Education and Income Predict Future Emotional Well-Being of Whites but Not Blacks: A Ten-Year Cohort. Brain Sci. 2018; 8.
- Assari S, Caldwell C, Bazargan M. Parental educational attainment and relatives’ substance use of American youth: Hispanics Diminished Returns. J Biosci Med (Irvine). 2020; 8: 122-134.
- Boyce S, Bazargan M, Caldwell CH, Zimmerman MA, Assari S. Parental Educational Attainment and Social Environment of Urban Public Schools in the U.S.: Blacks’ Diminished Returns. Children. 2020; 7: 44.
- Assari S, Boyce S, Caldwell CH, Bazargan M, Mincy R. Family Income and Gang Presence in the Neighborhood: Diminished Returns of Black Families. Urban Science. 2020; 4: 29.
- Shervin A. Parental Education and Spanking of American Children: Blacks’ Diminished Returns. World journal of educational research (Los Angeles, Calif). 2020; 8.
- Assari S. Family Socioeconomic Status and Exposure to Childhood Trauma: Racial Differences. Children. 2020; 7: 57.
- Kim P, Evans GW, Angstadt M, et al. Effects of childhood poverty and chronic stress on emotion regulatory brain function in adulthood. Proc Natl Acad Sci USA. 2013; 110: 18442-18447.
- Oshri A, Hallowell E, Liu S, et al. Socioeconomic hardship and delayed reward discounting: Associations with working memory and emotional reactivity. Dev Cogn Neurosci. 2019; 37: 100642.
- Yu M, Linn KA, Shinohara RT, et al. Childhood trauma history is linked to abnormal brain connectivity in major depression. Proc Natl Acad Sci USA. 2019; 116: 8582-8590.
- Assari S, Caldwell CH. Family Income at Birth and Risk of Attention Deficit Hyperactivity Disorder at Age 15: Racial Differences. Children (Basel). 2019; 6.
- Assari S, Boyce S, Bazargan M, Caldwell CH. African Americans’ Diminished Returns of Parental Education on Adolescents’ Depression and Suicide in the Adolescent Brain Cognitive Development (ABCD) Study. European Journal of Investigation in Health, Psychology and Education. 2020; 10: 656- 668.
- Akinhanmi MO, Biernacka JM, Strakowski SM, et al. Racial disparities in bipolar disorder treatment and research: a call to action. Bipolar Disord. 2018; 20: 506-514.
- Assari S, Caldwell CH, Zimmerman MA. Family Structure and Subsequent Anxiety Symptoms; Minorities’ Diminished Return. Brain Sci. 2018; 8.
- Assari S, Caldwell CH, Bazargan M. Association Between Parental Educational Attainment and Youth Outcomes and Role of Race/Ethnicity. JAMA Netw Open. 2019; 2: e1916018.
- Assari S, Mistry R, Bazargan M. Race, Educational Attainment, and E-Cigarette Use. Journal of Medical Research and Innovation. 2020; 4: e000185-e000185.
- Assari S, Mistry R, Caldwell CH, Bazargan M. Protective Effects of Parental Education Against Youth Cigarette Smoking: Diminished Returns of Blacks and Hispanics. Adolesc Health Med Ther. 2020; 11: 63-71.
- Assari S, Caldwell CH, Mincy R. Family Socioeconomic Status at Birth and Youth Impulsivity at Age 15; Blacks’ Diminished Return. Children (Basel). 2018; 5.
- Assari S. Family Socioeconomic Position at Birth and School Bonding at Age 15; Blacks’ Diminished Returns. Behav Sci (Basel). 2019; 9.
- Assari S, Boyce S, Bazargan M, Caldwell CH. Diminished Returns of Parental Education in Terms of Youth School Performance: Ruling out Regression toward the Mean. Children. 2020; 7: 74.
- Assari S. Parental Education on Youth Inhibitory Control in the Adolescent Brain Cognitive Development (ABCD) Study: Blacks’ Diminished Returns. Brain Sci. 2020; 10.
- Assari S, Lankarani MM. Race and Urbanity Alter the Protective Effect of Education but not Income on Mortality. Front Public Health. 2016; 4: 100.
- Healthy People 2020.
- Assari S. Life Expectancy Gain Due to Employment Status Depends on Race, Gender, Education, and Their Intersections. J Racial Ethn Health Disparities. 2018; 5: 375-386.
- Assari S, Boyce S, Akhlaghipour G, Bazargan M, Caldwell CH. Reward Responsiveness in the Adolescent Brain Cognitive Development (ABCD) Study: African Americans’ Diminished Returns of Parental Education. Brain Sciences. 2020; 10: 391.
- Assari S, Akhlaghipour G, Boyce S, Bazargan M, Caldwell CH. African American Children’s Diminished Returns of Subjective Family Socioeconomic Status on Fun Seeking. Children. 2020; 7: 75.
- Assari S. Youth Social, Emotional, and Behavioral Problems in the ABCD Study: Minorities’ Diminished Returns of Family Income. J Econ Public Financ. 2020; 6: 1-19.
- Assari S, Boyce S, Bazargan M. Subjective Family Socioeconomic Status and Adolescents’ Attention: Blacks’ Diminished Returns. Children. 2020; 7: 80.
- Assari S, Boyce S, Caldwell CH, Bazargan M. Minorities’ Diminished Returns of Parental Educational Attainment on Adolescents’ Social, Emotional, and Behavioral Problems. Children (Basel). 2020; 7.
- Assari S, Boyce S, Bazargan M, Caldwell CH. A Dream Deferred: African American Women’s Diminished Socioeconomic Returns of Postponing Childbearing from Teenage to Adulthood. Reproductive Medicine. 2020; 1: 62-76.
- Garavan H, Bartsch H, Conway K, et al. Recruiting the ABCD sample: Design considerations and procedures. Dev Cogn Neurosci. 2018; 32: 16-22.
- Auchter AM, Hernandez Mejia M, Heyser CJ, et al. A description of the ABCD organizational structure and communication framework. Dev Cogn Neurosci. 2018; 32: 8-15.
- Feldstein Ewing SW, Bjork JM, Luciana M. Implications of the ABCD study for developmental neuroscience. Dev Cogn Neurosci. 2018; 32: 161-164.
- Karcher NR, Barch DM. The ABCD study: understanding the development of risk for mental and physical health outcomes. Neuropsychopharmacology. 2020.
- Assari S, Currey TJ. Parental Education Ain’t Enough: A Study of Race (Racism), Parental Education, and Children’s Thalamus Volume. Journal of education and culture studies. 2021; 5.
- Assari S. Race, Ethnicity, Family Socioeconomic Status, and Children’s Hippocampus Volume. Research in health science. 2020; 5: 25.
- Assari S. Parental Education, Household Income, and Cortical Surface Area among 9-10 Years Old Children: Minorities’ Diminished Returns. Brain Sci. 2020; 10.
- Assari S, Boyce S, Bazargan M, et al. Parental Educational Attainment, the Superior Temporal Cortical Surface Area, and Reading Ability among American Children: A Test of Marginalization-Related Diminished Returns. Children (Basel). 2021; 8.
- Assari S, Boyce S. Race, Socioeconomic Status, and Cerebellum Cortex Fractional Anisotropy in Pre-Adolescents. Adolescents. 2021; 1: 70-94.
- Waldstein SR, Dore GA, Davatzikos C, et al. Differential Associations of Socioeconomic Status With Global Brain Volumes and White Matter Lesions in African American and White Adults: the HANDLS SCAN Study. Psychosom Med. 2017; 79: 327-335.
- Maharlouei N, Cobb S, Bazargan M, Assari S. Subjective Health and Happiness in the United States: Gender Differences in the Effects of Socioeconomic Status Indicators. J Ment Health Clin Psychol. 2020; 4: 8-17.
- Assari S. Race, Ethnicity, Family Socioeconomic Status, and Children’s Hippocampus Volume. Res Health Sci. 2020; 5: 25-45.
- Chalian H, Khoshpouri P, Assari S. Patients’ age and discussion with doctors about lung cancer screening: Diminished returns of Blacks. Aging Medicine. 2019; 2: 35-41.
- Assari S, Lankarani MM. Reciprocal Associations between Depressive Symptoms and Mastery among Older Adults; Black-White Differences. Front Aging Neurosci. 2016; 8: 279.
- Assari S. General Self-Efficacy and Mortality in the USA; Racial Differences. J Racial Ethn Health Disparities. 2017; 4: 746-757.
- Assari S. Whites but Not Blacks Gain Life Expectancy from Social Contacts. Behav Sci (Basel). 2017; 7.
- Assari S. Depressive Symptoms Increase the Risk of Mortality for White but Not Black Older Adults. Healthcare (Basel). 2018; 6.
- Assari S, Burgard S. Black-White differences in the effect of baseline depressive symptoms on deaths due to renal diseases: 25 year follow up of a nationally representative community sample. J Renal Inj Prev. 2015; 4: 127-134.
- Assari S, Lankarani MM, Burgard S. Black-white difference in long-term predictive power of self-rated health on all-cause mortality in United States. Ann Epidemiol. 2016; 26: 106-114.
- Assari S. Race, sense of control over life, and short-term risk of mortality among older adults in the United States. Arch Med Sci. 2017; 13: 1233-1240.
- Hudson D, Sacks T, Irani K, Asher A. The Price of the Ticket: Health Costs of Upward Mobility among African Americans. Int J Environ Res Public Health. 2020; 17.
- Bjork JM, Straub LK, Provost RG, Neale MC. The ABCD study of neurodevelopment: Identifying neurocircuit targets for prevention and treatment of adolescent substance abuse. Curr Treat Options Psychiatry. 2017; 4: 196-209.
- Casey BJ, Cannonier T, Conley MI, et al. The Adolescent Brain Cognitive Development (ABCD) study: Imaging acquisition across 21 sites. Dev Cogn Neurosci. 2018; 32: 43-54.
- Hagler DJ, Jr., Hatton S, Cornejo MD, et al. Image processing and analysis methods for the Adolescent Brain Cognitive Development Study. Neuroimage. 2019; 202: 116091.
- Lynam DR, Smith GT, Whiteside SP, Cyders MA. The UPPS-P: Assessing five personality pathways to impulsive behavior. West Lafayette, IN: Purdue University. 2006.
- Adams ZW, Kaiser AJ, Lynam DR, Charnigo RJ, Milich R. Drinking motives as mediators of the impulsivity-substance use relation: pathways for negative urgency, lack of premeditation, and sensation seeking. Addict Behav. 2012; 37: 848-855.
- Kaiser AJ, Milich R, Lynam DR, Charnigo RJ. Negative urgency, distress tolerance, and substance abuse among college students. Addict Behav. 2012; 37: 1075-1083.
- Chester DS, Lynam DR, Milich R, DeWall CN. Craving versus control: Negative urgency and neural correlates of alcohol cue reactivity. Drug Alcohol Depend. 2016; 163: S25-28.
- Chester DS, Lynam DR, Milich R, Powell DK, Andersen AH, DeWall CN. How do negative emotions impair self-control? A neural model of negative urgency. Neuroimage. 2016; 132: 43-50.
- Chester DS, Lynam DR, Milich R, DeWall CN. Social rejection magnifies impulsive behavior among individuals with greater negative urgency: An experimental test of urgency theory. J Exp Psychol Gen. 2017; 146: 962- 967.
- Peters JR, Derefinko KJ, Lynam DR. Negative Urgency Accounts for the Association Between Borderline Personality Features and Intimate Partner Violence in Young Men. J Pers Disord. 2017; 31: 16-25.
- Assari S. Racial Variation in the Association between Suicidal History and Positive and Negative Urgency among American Children. J Educ Cult Stud. 2020; 4: 39-53.
- Assari S. Racial Variation in the Association between Positive Urgency and Body Mass Index among American Children. Res Health Sci. 2020; 5: 129- 143.
- Assari S. Association Between Parental Educational Attainment and Children’s Negative Urgency: Sex Differences. Int J Epidemiol Res. 2021; 8: 14-22.
- Hu J, Kind AJ, Nerenz D. Area deprivation index predicts readmission risk at an urban teaching hospital. American Journal of Medical Quality. 2018; 33: 493-501.
- Assari S. Unequal Gain of Equal Resources across Racial Groups. Int J Health Policy Manag. 2017; 7: 1-9.
- Assari S. Health Disparities due to Diminished Return among Black Americans: Public Policy Solutions. Social Issues and Policy Review. 2018; 12: 112-145.
- Farah MJ. The Neuroscience of Socioeconomic Status: Correlates, Causes, and Consequences. Neuron. 2017; 96: 56-71.
- Silvanto J, Pascual-Leone A. Why the assessment of causality in brain-behavior relations requires brain stimulation. Journal of cognitive neuroscience. 2012; 24: 775-777.
- Lawson GM, Duda JT, Avants BB, Wu J, Farah MJ. Associations between children’s socioeconomic status and prefrontal cortical thickness. Dev Sci. 2013; 16: 641-652.
- Sowell ER, Thompson PM, Welcome SE, Henkenius AL, Toga AW, Peterson BS. Cortical abnormalities in children and adolescents with attention-deficit hyperactivity disorder. Lancet. 2003; 362: 1699-1707.
- Sowell ER, Mattson SN, Kan E, Thompson PM, Riley EP, Toga AW. Abnormal cortical thickness and brain-behavior correlation patterns in individuals with heavy prenatal alcohol exposure. Cereb Cortex. 2008; 18: 136-144.
- Marshall AT, Betts S, Kan EC, McConnell R, Lanphear BP, Sowell ER. Association of lead-exposure risk and family income with childhood brain outcomes. Nat Med. 2020; 26: 91-97.
- Assari S, Boyce S, Bazargan M, Caldwell CH. Race, Socioeconomic Status, and Sex Hormones among Male and Female American Adolescents. Reprod Med (Basel). 2020; 1: 108-121.
- Assari S, Boyce S, Bazargan M, Caldwell CH, Zimmerman MA. Place- Based Diminished Returns of Parental Educational Attainment on School Performance of Non-Hispanic White Youth. Frontiers in Education. 2020; 5.
- Assari S. Parental Education and Spanking of American Children: Blacks’ Diminished Returns. World J Educ Res. 2020; 7: 19-44.
- Assari S, Caldwell CH, Mincy RB. Maternal Educational Attainment at Birth Promotes Future Self-Rated Health of White but Not Black Youth: A 15-Year Cohort of a National Sample. J Clin Med. 2018; 7.
- Assari S, Mardani A, Maleki M, Bazargan M. Black-White Differences in the Association between Maternal Age at Childbirth and Income. Women’s Health Bulletin. 2019; 6: 36-42.
- Assari S, Thomas A, Caldwell CH, Mincy RB. Blacks’ Diminished Health Return of Family Structure and Socioeconomic Status; 15 Years of Followup of a National Urban Sample of Youth. J Urban Health. 2018; 95: 21-35.
- Assari S, Gibbons FX, Simons R. Depression among Black Youth; Interaction of Class and Place. Brain Sci. 2018; 8.
- Assari S, Gibbons FX, Simons RL. Perceived Discrimination among Black Youth: An 18-Year Longitudinal Study. Behav Sci (Basel). 2018; 8.
- Assari S. Parental Education and Youth Inhibitory Control in the Adolescent Brain Cognitive Development (ABCD) Study: Blacks’ Diminished Returns. Brain Sciences. 2020; 10: 312.
- Assari S. Original Paper Are Teachers Biased against Black Children? A Study of Race, Amygdala Volume, and Problem Behaviors. 2021.
- Assari S. Racial Variation in the Association between Positive Urgency and Body Mass Index among American Children. Research in health science. 2020; 5: 129.
- Assari S, Lankarani MM, Caldwell CH. Does Discrimination Explain High Risk of Depression among High-Income African American Men? Behav Sci (Basel). 2018; 8.
- Moghani Lankarani M, Assari S. Diabetes, hypertension, obesity, and longterm risk of renal disease mortality: Racial and socioeconomic differences. J Diabetes Investig. 2017; 8: 590-599.
- Assari S, Caldwell CH. Social Determinants of Perceived Discrimination among Black Youth: Intersection of Ethnicity and Gender. Children (Basel). 2018; 5.
- Assari S, Boyce S, Bazargan M, Mincy R, Caldwell CH. Unequal Protective Effects of Parental Educational Attainment on the Body Mass Index of Black and White Youth. International Journal of Environmental Research and Public Health. 2019; 16: 3641.
- Assari S, Boyce S, Bazargan M, Caldwell CH. Mathematical Performance of American Youth: Diminished Returns of Educational Attainment of Asian- American Parents. Education Sciences. 2020; 10: 32.
- Assari S, Bazargan M. Protective Effects of Educational Attainment Against Cigarette Smoking; Diminished Returns of American Indians and Alaska Natives in the National Health Interview Survey. International Journal of Travel Medicine and Global Health. 2019.
- Assari S, Bazargan M. Education Level and Cigarette Smoking: Diminished Returns of Lesbian, Gay and Bisexual Individuals. Behav Sci (Basel). 2019; 9.
- Assari S. Education Attainment and Obesity Differential Returns Based on Sexual Orientation. Behav Sci (Basel). 2019; 9.
- Assari S. Income and Mental Well-Being of Middle-Aged and Older Americans: Immigrants’ Diminished Returns. International Journal of Travel Medicine and Global Health. 2020; 8: 37-43.
- Assari S. Socioeconomic Status and Current Cigarette Smoking Status: Immigrants’ Diminished Returns. Int J Travel Med Glob Health. 2020; 8: 66- 72.
- Assari S. Unequal Gain of Equal Resources across Racial Groups. Int J Health Policy Manag. 2018; 7: 1-9.
- Hudson DL, Bullard KM, Neighbors HW, Geronimus AT, Yang J, Jackson JS. Are benefits conferred with greater socioeconomic position undermined by racial discrimination among African American men? J Mens Health. 2012; 9: 127-136.
- Hudson DL, Neighbors HW, Geronimus AT, Jackson JS. The relationship between socioeconomic position and depression among a US nationally representative sample of African Americans. Soc Psychiatry Psychiatr Epidemiol. 2012; 47: 373-381.
- Hudson DL, Neighbors HW, Geronimus AT, Jackson JS. Racial Discrimination, John Henryism, and Depression Among African Americans. J Black Psychol. 2016; 42: 221-243.
- Determined Tb. Prevalence, Severity and Burden of Post-Traumatic Stress Disorder in Black Men and Women Across the Adult Lifespan. Journal of Aging and Health. 2022; In Press.
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