PURPOSE: To estimate the risk of schizophrenia in adulthood among children and adolescents with ADHD compared to the background population. SUBJECTS/MATERIALS AND METHODS: Two hundred and eight youths with ADHD (183 boys; 25 girls) were followed prospectively. Diagnoses of schizophrenia were obtained from The Danish Psychiatric Central Register. The relative risk (RR) of schizophrenia for cases with ADHD, compared to the normal population, was calculated as risk ratios. Hazard ratios (HR's) by Cox regression were calculated in the predictor analyses. RESULTS: Mean age for ADHD cases at follow-up was 31.1years. Schizophrenia diagnoses were given to 3.8% of these cases. Compared to the general population, RR of schizophrenia in cases with ADHD was 4.3 (95% CI 1.9-8.57). DISCUSSION AND CONCLUSION: This prospective follow-up study found children with ADHD to be at higher risk of later schizophrenia than controls. If replicated, these results warrant increased focus on the possible emergence symptoms of schizophrenia or schizophreniform psychosis during clinical follow-up of patients with ADHD.
European Psychiatry, 2014, Vol 29, Issue 4, p. 259-263