Understanding Psychiatric Comorbidity in the Natural History of Autism Spectrum Disorders

Editorial

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by the presence of persistent deficits in social communication and social interaction and restricted and repetitive patterns of behavior, interests or activities causing clinically significant impairment in several areas of functioning [1]. Several recent studies have highlighted that people with ASD, particularly high functioning individuals, are at high risk of comorbid psychopathology [2,3]. Evidence to date suggests that the management of behavioral problems in this clinical population is a challenge for clinicians and families, and comorbid disorders may cause clinical impairment and additional burden of illness. Literature studies have shown that the most frequent comorbid disorders with ASD are mood disorders, anxiety disorders, Obsessive Compulsive Disorders (OCD), and Attention Deficit And Hyperactivity Disorder (ADHD) [2,4-14]. For instance, Ghaziuddin et al. (1998) in a study examining the occurrence of psychiatric disorders in 35 patients with a diagnosis of Asperger syndrome, reported a mood disorder rate of 34% [12]. In line with these findings, in a recent study from our group, aimed at evaluating the prevalence of mood disorders in patients suffering from ASD, Major Depression (MD) or Typically Developing (TD) individuals, we found higher depressive symptoms in the ASD group as compared to the TD group, whereas no significant differences were found between the ASD and the MD group. Moreover, in the ASD group a higher level of depressive symptoms increased the risk of poorer global functioning. These results suggest that depressive symptoms in patients with ASD may be associated with a poorer global functioning, with a consequent impairment in the psychological profile and social adjustment, and should alert clinicians on the importance of assessing mood disorders in these patients in order to choose the appropriate treatment [4]. Another illustrative example is the comorbidity with obsessive-compulsive disorders: even though it is difficult to discriminate whether obsessive-compulsive symptoms are a separate comorbid condition, rather than a core symptom of ASD, studies have reported an association between these disorders [9,13]. For instance, Russell et al (2005) found that 25% of individuals with ASD also met the criteria for a diagnosis of OCD [9]. In 2010 we have published our experience on the association between OCD and ASD on the European Journal of Child and Adolescent Psychiatry, comparing children and adolescents with Asperger Syndrome (AS) to a matched OCD group and a TD group [14]. Children with AS showed higher frequencies of obsessive and compulsive symptoms as compared to typically developing children, and these features seem to cluster around hoarding behaviors. The level of insight resulted poor in both OCD and AS children.

Although the available data suggest that psychiatric comorbidity in ASD is a crucial issue, the prevalence rates for the various disorders are highly heterogeneous. For instance, studies published so far on the co-occurrence of ASD and mood disorders have reported prevalence rates ranging from 1.4% to 70% [6,15]. However, these studies included patients with ASD highly heterogeneous in terms of both age and severity of symptoms, thus it is very difficult to compare the results. Indeed, the manifestation and occurrence of psychiatric symptoms in this clinical population depends on a variety of factors, including age, severity of autistic behaviors, intellectual ability and adaptive functioning [16].

Moreover, different methodologies and diagnostic criteria were used in the studies cited above, as well as instruments developed and standardized for the general population, and likely not appropriate for ASD [2,4].

Autistic symptoms can mask psychiatric disorders in comorbidity and for this reason performing a diagnosis of psychiatric comorbidity in ASD can be a challenge for clinicians. Indeed, these patients often show a deficit in communicative abilities and "theory of mind", that in turns impair their capability of describing their own mental states, mental experiences as well as their own feelings and emotions, and this makes the clinicians' ability of recognizing comorbidities in ASD even more complicated [2].

Moreover, the threshold between autism spectrum core symptoms and comorbid psychiatric disorders can be blurred. For instance, a sudden decrease of repetitive or stereotyped behaviors in individuals with ASD could be mistakenly ascribed to an improvement of the autistic symptomatology; however it may also be the onset of depressive symptoms.

In conclusion, albeit recent studies have indicated that people with ASD often suffer from important comorbidities, psychiatric disorders are frequently misdiagnosed or unrecognized [17]. The need for a better understanding of the prevalence of these comorbidities in ASD compared to the general population or to other clinical psychiatric populations as well as of the natural history of the symptoms in comorbidity in persons with autism is extremely urgent. It is crucial to understand if the psychiatric symptoms observed in autistic persons during lifespan are part of the normal evolution of the autistic disorders or rather a different diagnostic psychiatric disorder. The diagnostic challenges of psychiatric symptoms in ASD have underlined the need of specific diagnostic criteria and proper screening tools, specifically designed for this population, with the purpose of helping clinicians to recognize comorbid disorders in people with ASD and promoting research to unify the methodology. Only longitudinal studies may allow to describe the developmental trajectories and to detect subtle changes in behavior at different stages of development.

Given that psychiatric comorbidities appear to be common in ASD, refining diagnosis in order to provide more specific treatments is a major issue for the mental health field. Shedding light on the clinical phenomenology of comorbid psychiatric symptoms in ASD and defining their presentation and course would contribute to the development of appropriate early intervention and treatment strategies.

References

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