Klinefelter syndrome and risk of psychosis, autism and ADHD

Background: Schizophrenia, bipolar disorder, autism spectrum disorders and ADHD might be over-represented in Klinefelter syndrome, but previous investigations have yielded inconclusive results. Methods: We compared a national sample of 860 Klinefelter patients in Sweden with 86 000 matched population controls. To assess the risks of schizophrenia, bipolar disorder, autism spectrum disorder and ADHD in Klinefelter patients, we estimated odds ratios and 95% confidence intervals using conditional logistic regressions. Results: Klinefelter patients had almost four times higher risks of schizophrenia, odds ratio (OR) = 3.6, 95% confidence interval (CI) 2.0-6.7 and bipolar disorder (OR = 3.8, CI 1.8-7.6) and about six times higher risk of autism spectrum disorder (OR = 6.2, Cl 4.0-9.4) and ADHD (OR = 5.6, CI 4.0-7.8). Conclusions: The risk of psychosis, autism and ADHD is increased in Klinefelter patients. These findings indicate an X chromosome-related factor in the etiology of the studied psychiatric disorders, and may also have implications for treatment of patients with Klinefelter syndrome. (C) 2013 Elsevier Ltd. All rights reserved.