Abstract
Schizophrenia (SCZ) and other psychotic disorders are often preceded by behavioral abnormalities in early life that overlap with symptoms of neurodevelopmental disorders such as autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). It is unclear, however, to what extent ASD and ADHD predict conversion from this clinical high-risk (CHR) phase to syndromal psychosis. We investigated these associations in a cohort of 151 CHR individuals. We hypothesized that ASD and ADHD would predict conversion at a diagnostic level, and that impaired social communication and inattention would be the strongest predictors at a symptom level. We fit regression models that included relevant characteristics reported at time of initial evaluation for CHR as predictors — ASD and ADHD diagnosis; childhood social problems, repetitive behaviors, and attention problems; hypersensitivity to light, sound, and touch; sex; age; race; ethnicity; and psychiatric history in a first-degree relative — with conversion to syndromal psychosis within two years as the outcome. Childhood repetitive behaviors (OR 15.74, 95% CI 1.62–383.72, p = 0.0328), ADHD diagnosis (OR 4.15, 95% CI 1.31–14.05, p = 0.0177), and male sex (OR 3.39, 95% CI 1.44–8.64, p = 0.0071) were significant predictors. Childhood repetitive behaviors, but not social problems, predicting conversion was unexpected; although this could relate, in part, to repetitive behavior being much less common than social problems in our sample. The ADHD finding is consistent with data showing genetic and epidemiological overlap between ADHD and SCZ and raises questions for future research about which aspects of ADHD may drive this association.