Autistic Traits in Psychotic Disorders: A Large-Scale Comparison across Patients, Siblings and Typical Comparisons and Impact on Social Functioning

Background: Autism traits are present at elevated rates in individuals with psychotic disorders (PD). However, prevalence varies across clinical samples and it is unclear whether individuals with a genetic risk for psychosis (GR) also report more symptoms. Furthermore, it is unknown to what extent comorbid autism symptoms may have an impact on social functioning in psychotic disorders.

Objectives: To address these questions in a large sample of 504 individuals with a PD, 572 individuals with GR (siblings) and 337 typical comparison (TC) individuals

Methods: Autism traits were assessed with the Autism Spectrum Quotient (AQ) and social functioning was measured with the Social Functioning Scale.

Results: The proportion of AQ scores >32 (indicative of autism diagnosis) was 6.6% for PD, 1.1% for GR and 1.2% for TC. For AQ scores >26 (indicative of high autism traits) respective percentages were: 21.4%, 2.8% and 2.4%. Mean group differences for autism traits (PD > GR > TC) and social functioning (PD < GR < TC) were all significant, albeit with small effect sizes for GR vs TC. Within the PD and GR group, autistic traits showed a negative impact on overall social functioning above and beyond the effect of positive psychotic symptoms.

Conclusions: At least 1 in 5 individuals with a psychotic disorder is characterised by elevated levels of autism traits. In addition, levels of social functioning are negatively affected by autisms traits in individuals with (a genetic predisposition to) psychotic disorders. These findings warrant specific clinical guidelines for psychotic patients who present themselves with autistic comorbidity.