Large outcome studies or systematic clinical surveys of adult ASDs are few. To our knowledge, this is one of the first such studies presenting detailed clinical data on a large consecutive group of adults with ASDs and normal intelligence. It includes a wide age span (16–60 yrs), with a relatively large proportion of subjects over 30 yrs of age (42%), and a substantial representation of women.
The purpose of describing the presence of autistic disorder symptoms in all three diagnostic subgroups was to address the important question of the adequacy of the current DSM-IV ASD categories. The interpretation of different patterns of criteria in the three diagnostic groups first has to consider that these criteria were used to assign the diagnoses. Then, as expected, the small group with normal-intelligence AD (equivalent to HFA) had the most pervasive ASD symptomatology, followed by the AS group, while the PDD NOS group exhibited the least number of symptoms. However, one-third of the PDD NOS patients and half of the AS patients met the DSM-IV communication criterion despite the fact that, according to the DSM-IV, only "subtle aspects of social communication" is expected to be impaired in AS, and the criteria for PDD NOS do not even require communication problems. When comparing the distribution of G & G criteria across the subgroups, deficits in the area of "social interaction" were evident in all ASD cases, while the other criteria were all more pronounced in the AS group as compared to the PDD NOS group. A tentative conclusion would be that these findings fit a dimensional model of ASDs and that the high rates for all criteria across the diagnostic categories would speak against their use as differential diagnostic entities.
The proportion of female subjects was high in this consecutively recruited clinical group compared to epidemiological studies [4
]. This high representation could suggest that women with ASDs develop more severe social deficits [31
] or more concomitant psychopathology. In a group of children and young adults diagnosed with normal-intelligence ASDs, Holtmann and colleagues [5
] did not find sex differences in the triad of autism core dysfunctions. Our findings can extend this to an older group of patients.
It is worth noting that referral practices are likely to have enriched our study group with a higher prevalence of comorbid conditions in comparison to the ASD population as a whole. Indeed, many of our patients had previously been in contact with specialists in psychiatry and were then referred to our expert centers. The prevalence of comorbid conditions is also likely to be inflated by our decision to disregard DSM-IV criteria excluding certain diagnoses in the presence of ASD. Nonetheless, this decision was justified by our aim to describe clinical conditions where prevalence would have been zero if strict hierarchical criteria had been followed.
High comorbidity with childhood-onset disorders was expected in our study population. Despite the fact that the current diagnostic classification of ASDs precludes a diagnosis of concomitant ADHD (in DSM-IV) or hyperkinetic disorder (in ICD-10), earlier estimates have reported very high rates of these problems (80–83%) in children with ASDs [4
]. In our group, the rate was lower but still substantial. The most common ADHD subtypes were the combined and inattentive forms, which may be due to the different presentation of ADHD in adulthood.
] suggested that the features of the autistic syndrome, for example insistence on sameness, were related to anxiety. Other authors have described patients with ASD as vulnerable to stress because of a restricted repertoire of appropriate coping mechanisms [33
]. In agreement with this, anxiety disorders, especially OCD where rates were very similar to a recent study of mostly AS patients [34
], were clearly overrepresented as compared to the general population.
Earlier estimates of comorbid depression in autism and AS vary widely, from 4 to 38% [35
]. Our high frequency of major depressive disorder might be linked to the higher median age in our study group. This finding and the fact that only a minority of the patients had ever had antidepressant treatment would stress the importance of attention to such symptoms in this patient category. The overlap of symptoms between ASDs and depression (e.g. social withdrawal, impaired non-verbal communication) can make diagnoses difficult, and earlier studies have pointed out the difficulties these patients have in verbalizing their changes in mood and describing depression [36
Psychotic symptoms in ASDs are controversial. Since our study group was clinically recruited, it cannot be considered to be representative for a general ASD population, but the need for revision of the criteria precluding or diffusing the diagnostic possibilities in this field is obvious.
Substance-related disorders, especially those related to alcohol, were no more common in this group than in the general population, but more prevalent among subjects diagnosed with a PDD NOS than among subjects with AS. This, and the fact that antisocial PD was found only in the PDD NOS group, is in line with other studies describing a subgroup of antisocial individuals having atypical autistic features presenting as PDD NOS [37
Patients afflicted with ASDs often describe themselves in clinical interviews or in self-rate questionnaires in a way that corresponds to PD characteristics [38
]. Our findings, with two-thirds of our subjects meeting criteria for at least one PD, confirm this, as well as a preponderance of OCPD and avoidant PDs [20
]. Furthermore, the higher rate of OCPD in AS compared to PDD NOS corresponds to the AS group's higher rate of restrictions in repertoires and interests. However, the AS group did not have a higher rate of OCD as compared to the PDD NOS group. Despite the tendency toward more diagnoses of cluster A and C in the total group, the overall conclusion is that categorical PDs provide a rather unspecific description of the maladaptive patterns of personality function in the ASD group.
A large proportion of the subjects, especially the females, had been bullied during their school years. In spite of high levels of education, more than half of the entire ASD group was unemployed, on sick-leave, or had a medical pension. Some 40% were still living with their parents or in community-based group homes. In line with previous studies, only a few had ever had a long-term relationship [5
], though marriage or cohabitation was slightly more common among the women. Altogether, the outcome must be considered rather poor, taking the high intellectual ability of the group into account.