Psychiatric comorbidity in young adults with a clinical diagnosis of Asperger syndrome

Abstract

In children with autism spectrum disorders, previous studies have shown high rates of psychiatric comorbidity. To date, studies on adults have been scarce. The aim of the present study was to investigate psychiatric comorbidity in young adults with Asperger syndrome. Participants were 26 men and 28 women (mean age 27 years) with a clinical diagnosis of Asperger syndrome. Psychiatric comorbidity was assessed by the Structured Clinical Interview for DSM-IV Axis I Disorders. IQ was measured using the Wechsler Adult Intelligence Scale, Third Edition. Autism spectrum diagnoses were confirmed using the DIagnostic Interview for Social and Communication Disorders. In our study group, 70% had experienced at least one episode of major depression, and 50% had suffered from recurrent depressive episodes. Anxiety disorders were seen in about 50%. Psychotic disorders and substance-induced disorders were uncommon. In conclusion, young adults with autism spectrum disorders are at high risk for mood and anxiety disorders. To identify these conditions and offer treatment, elevated vigilance is needed in clinical practice.

Introduction

Autism-spectrums disorders (ASDs), classified as pervasive developmental disorders (PDDs) in the DSM-IV (APA, 2000), are relatively common social communication disorders that affect about 0.6–1% of the general population (Baird et al., 2006, Fernell and Gillberg, 2010). ASDs share a core triad of abnormalities: (1) qualitative impairments in reciprocal social interactions, (2) qualitative impairments in verbal and non-verbal communication, and (3) restricted social imagination with repetitive and stereotyped patterns of interests and behaviour. The DSM-IV includes autistic disorder (AD) (pervasive deficits in all three domains), Asperger syndrome (AS) (pervasive deficits in social interaction and behaviours in the presence of superficially normal expressive verbal development) and pervasive developmental disorder not otherwise specified (PDD-NOS) (not meeting full criteria for either AD or AS, but with pervasive deficit in social interaction). High-functioning autism (HFA) is a diagnostic term sometimes used to describe individuals with AD with low normal or normal intelligence, but it is a misnomer, particularly because in HFA, “the autism” is not high-functioning, even though the individual may, occasionally, have high intellectual functioning. Researchers comparing AS and HFA have found no important differences, implying that the boundaries within the autism spectrum are not clear (Howlin, 2003). However, some researchers still consider a separation of AS from autism to be clearly motivated, particularly on the basis of discriminative results on neurobiological parameters (Yu, Cheung, Chua, & McAlonan, 2011).

After the inclusion of AS in DSM-IV in 1994, and with better knowledge and awareness about ASD among professionals and the general population, the recognition and clinical diagnosis of individuals with AS/HFA have increased considerably in recent years (Baird et al., 2006). In Sweden, diagnostic assessment of children with ASDs and other neurodevelopmental problems has been available in child psychiatric health care since the beginning of the 1990s. In adult psychiatric health care, however, diagnostic evaluation of developmental disorders has not come to the forefront until the last five years.

There is growing evidence that people with ASDs are at high risk of associated psychiatric disorder, particularly depression and anxiety (Ghaziuddin, 2002, Skokauskas and Gallagher, 2010, Stewart et al., 2006, Sverd, 2003, Wing, 1981). However, research has been conducted mostly on children and adolescents (Mattila et al., 2010, Simonoff et al., 2008), and on adults with associated learning disability (LoVullo & Matson, 2009). Very few investigations on adults with ASD and normal intellectual ability have been carried out. Current depression was suggested to be present in a large minority of adults with AS/HFA using the self-report Beck Depression Inventory (Cederlund et al., 2010, Hill et al., 2004). By using Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I), Hofvander et al. (2009) showed that about 50% in their study group had a lifetime diagnosis of mood disorder. Another Swedish study found 15% of a tertiary referral group of patients with ASD had bipolar or psychotic disorder (Stahlberg, Soderstrom, Rastam, & Gillberg, 2004). Moderately high rates of other axis-I disorders assessed with SCID-I have also been reported in an investigation on insomnia in 20 individuals with AS, however some exclusion criteria (e.g. no medication) had probably influenced the results (Tani et al., 2003). Sterling et al. found depressive symptoms in about 40% of their clinically referred group of 46 cases with ASD, using a psychiatric history interview similar to the SCID-I, but the recruitment of subjects was not clearly stated (Sterling, Dawson, Estes, & Greenson, 2008). To sum up, very few investigations on clinically relevant systematically examined psychiatric comorbidity in adults with ASD and normal intellectual ability have been undertaken. We have been unable to locate even one such study specifically referring to individuals with clinically diagnosed Asperger syndrome. The selection of participants and measurements has varied considerably across the small number of published studies, making head-to-head comparisons impossible. All the published studies relate to clinic referral studies. No previous study, except the one by Cederlund et al. (2010) has attempted to demonstrate the basis for any generalisability of the results obtained.

The purpose of the present study was to systematically examine psychiatric axis-I-comorbidity in adult individuals, both men and women, with a clinically established diagnosis of AS. The aim was to include a reasonably large sample from a defined geographic area, and one that could be well-defined regarding ASD diagnostics, intellectual ability and clinical representativity.