Psychotic-Like Experiences and Common Mental Disorders in childhood and adolescence: bidirectional and transdiagnostic associations in a longitudinal community-based study

Psychotic-like Experiences (PE) in early adolescence may increase the risk for later psychotic and non-psychotic disorders. Common psychiatric disorders may also increase the risk of PE later in life. We aim to explore bidirectional associations of PE and common mental disorders among 1,712 youth from a 3-year follow-up community-based study. At baseline, we evaluated 6-12 years old subjects using dimensional and categorical measures of PE by self-reports and clinician ratings. Common mental disorders were assessed by structured interviews grouped into DSM-based categories (Depressive, Anxiety, Attention Deficit Hyperactivity Disorder (ADHD) and Disruptive Behavior Disorders) and Common Adolescent Behaviors (Substance Use and Self-harm). Subjects were reassessed with the same instruments after 3 years. Our study suggests an association between PE variables over time. A total of 15.9% (n = 272) participants scored above cutoff values at baseline and an increased proportion of 20.9% (n = 358) remained positive after follow-up. We also found bidirectional associations between PE and Common Mental Disorders. Baseline PE increased the risk of Depressive Disorders, Substance Use, and Self-harm, whereas baseline ADHD was associated with later PE. Comorbidity analyses showed significant relationships in both directions, with increased risk of PE according to the number of comorbid psychiatric disorders. We showed that subthreshold psychotic symptoms predict subsequent Depressive Disorders and that, reciprocally, other comorbid psychiatric disorders, such as ADHD, can predict its future expression. These findings suggest PE might be a part of a shared psychiatric vulnerability continuum, with distinct phenotypes over development.