Psychosis and adult Attention Deficit Hyperactivity Disorder (ADHD) have shared attributes, but evidence that they are associated is sparse and inconsistent.

We tested hypotheses that 1] adult ADHD symptoms are associated with psychosis and individual psychotic symptoms 2] links between ADHD symptoms and psychosis are mediated by prescribed ADHD medications, use of illicit drugs, and dysphoric mood (depression and anxiety).

The Adult Psychiatric Morbidity Survey 2007 (N=7403) provided data for regression and multiple mediation analyses. ADHD symptoms were coded from the ADHD Self-Report Scale (ASRS). Dependent variables comprised auditory hallucinations, paranoid ideation, and identified psychosis.

Higher ASRS total score was significantly associated with psychosis (O.R: 1.11; 95% CI 1.02-1.20; p = 0.013), paranoid ideation (O.R:1.12; CI 1.09-1.14; p<0.001) and auditory hallucinations (O.R 1.11; CI 1.08-1.15; p<0.001) even after controlling for socio-demographic variables, verbal IQ, autism spectrum disorder traits, childhood conduct problems, hypomanic mood and dysphoric mood. The link between higher ADHD symptoms and psychosis variables was significantly mediated by dysphoric mood (psychosis, 21%; paranoid ideation, 23%; auditory hallucination, 11%), but not by prescribed ADHD medication or use of amphetamine, cocaine or cannabis.

Higher levels of adult ADHD symptoms and psychosis are linked, and dysphoric mood may form part of the mechanism. Those with greater levels of ADHD symptoms in adulthood may be at higher risk of psychosis. Our analyses contradict the clinical view that the main explanation for people with ADHD symptoms developing psychosis is abuse of illicit drugs or ADHD medications.