Overlapping symptoms of attention deficit hyperactivity disorder ( ADHD ), autism, and personality disorder in a community sample

OBJECTIVES: Attention deficit hyperactivity disorder (ADHD), autism, and personality disorder (PD) often present with overlapping symptom profiles, complicating diagnostic assessment and treatment planning. Yet, few studies have examined the extent and nature of these overlaps, or the mechanisms that may underpin them. The current study aimed to address this gap by investigating overlapping symptom profiles of ADHD, autism, and PD, and the potential transdiagnostic mechanisms contributing to such in a community sample. DESIGN AND METHODS: A total of 512 adults with a history of mental health diagnosis residing in the United States or United Kingdom completed self-report questionnaires assessing ADHD, autism, and PD symptoms, alongside measures of adverse childhood experiences, executive functioning, and mentalization. RESULTS: We found substantial symptom overlap across ADHD, autism, and PD, with executive functioning emerging as the strongest predictor of shared variance. CONCLUSIONS: Given symptom overlaps in areas related to interpersonal, behavioural, and emotional control, we propose that self-regulation may underlie the common symptoms of ADHD, autism, and PD. Finally, our results support the integration of neurodevelopmental conditions into broader models of psychopathology structure, such as the Hierarchical Taxonomy of Psychopathology (HiTOP), and highlight specific symptom dimensions that can help differentiate between these conditions.