Background. There is substantial evidence that the genetic liability to autism confers a risk for a range of more subtle social and communication impairments, as well as stereotyped and repetitive behaviours. Recent research suggests that increased expression of particular personality traits may be a manifestation of the liability to autism. Methods. To investigate this we examined the personality traits of the adult relatives of 99 autistic and 36 Down's syndrome probands, using the informant version of the Modified Personality Assessment Schedule. Results. There was significantly increased expression of the traits anxious, impulsive, aloof, shy, over-sensitive, irritable and eccentric among the autism relatives with evidence of different profiles for male and female relatives and for parents and adult children. Factor analysis revealed three broad groups of traits, two of which (‘withdrawn’ and ‘difficult’) appeared to reflect impairments in social functioning and a third group of anxiety related traits (‘tense’). Each of these factors differed in their pattern of associations with the factor we termed ‘withdrawn’ showing a similar pattern of association to that found for other autism related conditions. The ‘tense’ factor appeared in part to be related to the burden of caring for an autistic child. Conclusions. This study confirms the finding that particular personality traits may aggregate in the family members of autistic individuals and furthermore that some of these traits may be a manifestation of the liability to autism.

Background. The liability to autism confers a risk for a range of more subtle autistic-like impairments, but it remains unclear whether it also confers a risk for other psychiatric disturbances.Methods. To investigate this, we studied the pattern of familial aggregation of psychiatric disorders in relatives of 99 autistic and 36 Down's probands, using family history and direct interview measures.Results. Family history data showed that motor ties, obsessive-compulsive (OCD) and affective disorders were significantly more common in relatives of autistic probands and that individuals with OCD were more likely to exhibit autistic-like social and communication impairments. Direct interview data confirmed the increased rate of affective disorders (especially major depressive disorder) in the first-degree relatives. There was no evidence to indicate significant co-morbidity between affective disorders and the broadly defined phenotype of autism. Moreover, the characteristics of the probands' and the relatives' that were associated with the liability to familiality of the broader phenotype of autism differed from those that predicted the liability to the familiality of affective disorders. Examination of the onset of affective disorders suggested that the increased risk was not confined to the period following the birth of the child with autism.Conclusions. Overall, the results indicated that OCD, but not affective disorders, may index an underlying liability to autism. They also indicated that the increased risk of affective disorders was not solely the consequence of the stress of raising a child with autism and that further research will be required to clarify the mechanisms involved.

Objective: To determine whether and why obstetric complications are associated with autism.Method: Obstetric histories, obtained at maternal interview and coded as an optimality score (OS), were compared in two groups: 78 families containing an autistic proband (ICD-10 criteria) and 27 families containing a Down syndrome (DS) proband. The OS was examined in relation to offspring diagnosis, proband characteristics, and familial loading for autism and its phenotypic variants.Results: Autistic and DS probands had a significantly elevated OS compared with unaffected siblings, regardless of birth order position. The elevation was mainly due to an increase in mild as opposed to severe obstetric adversities. In autistic probands, the OS was best predicted by familial loading for autism and its phenotypic variants, but in the absence or this measure by the number of autistic symptoms. Among siblings of autistic probands affected with autism or its variants, the OS was best predicted by the probands' OS, and in its absence, by the measure of familial loading. In DS probands and siblings the OS was associated with increased maternal age, although this did not account for the OS elevation in DS probands.Conclusions: Rather than praying any principal ethological role, the obstetric adversities associated with autism either represent an epiphenomenon of the condition or derive from some shared risk factor(s).

Early screening studies of autistic individuals suggested that up to one-quarter of cases were associated with the Fragile X anomaly. Recent studies find that the usual behavioural phenotype of the Fragile X anomaly is distinct from autism as usually defined, and that a variety of methodological factors contribute to the variability of the prevalence estimates. We report the prevalence of the Fragile X anomaly, using strict cytogenetic criteria, in a large sample of autistic individuals whose diagnosis was confirmed using a standardised diagnostic instrument. The anomaly was detected in 1.6% of tested autistic individuals from a combined sample of: autistic twins; clinic attenders; and, individuals from families multiplex for autism or related cognitive phenotypes. The anomaly was not detected in greater than 2.5% of any of the constituent samples and accounted for only a small proportion of the genetic influences amongst concordant twins and multiplex families. The anomaly was detected in 5% of the 40 tested autistic females, confirming reports that the prevalence of the anomaly is similar amongst autistic individuals of both sexes.