Autism spectrum traits in adults with attention-deficit/hyperactivity disorder (ADHD): a hidden multifaceted phenotype marked by affective comorbidity, emotional dysregulation, and chronobiological disturbances.

Background: Autism spectrum disorder (ASD) is a commonly observed comorbidity in children with attention-deficit/hyperactivity disorder (ADHD). Nevertheless, the impact of autism spectrum traits on clinical presentation and comorbidities in adults with ADHD remains largely underexplored.

Methods: 105 adults with ADHD were recruited at the outpatient service of the Psychiatry Unit 2 at Pisa University Hospital and subdivided according to screening for ASD based on the Autism-Spectrum Quotient (AQ). Comparative analyses were performed for sociodemographic and clinical variables.

Results: Participants with a positive screening for ASD (N = 23, 21.9%) were more frequently females, had a higher age at first clinical referral, higher comorbidity rates with mood and anxiety disorders, particularly social anxiety, and a lower rate of cannabis use disorder. They showed significantly greater severity of ADHD and emotional dysregulation, worse personality and interpersonal functioning, more depressive, cyclothymic and anxious temperamental dispositions, more pathological personality traits, increased biological rhythm disturbances and evening chronotype.

Conclusions: Autism spectrum traits are commonly reported in adults with ADHD and may be associated with female sex and a complex clinical presentation characterized by affective comorbidity, more severe emotional dysregulation and chronobiological disturbances.