Causal associations between schizophrenia and other psychiatric disorders: A Mendelian randomization study.

This genetic study found that people with a genetic risk for schizophrenia are more likely to also develop other conditions. The strongest link was with bipolar disorder (71% higher chance), followed by autism (17% higher chance) and alcohol problems (15% higher chance). There was also a very small link with depression. The study didn't find connections with ADHD, eating disorders, anxiety, or OCD.

This Mendelian randomization study investigated causal relationships between schizophrenia and eight psychiatric disorders using genetic data from large-scale genome-wide association studies. The analysis revealed that genetic predisposition to schizophrenia significantly increases the risk of developing bipolar disorder (70.7% increased odds), autism spectrum disorders (17.4% increased odds), and alcohol use disorder (14.5% increased odds). A statistically significant but clinically marginal association was found with depression. No causal relationships were detected with ADHD, anorexia nervosa, anxiety disorders, or obsessive-compulsive disorder.

Sensitivity analyses confirmed these findings, and reverse causation was ruled out through bidirectional testing.

Clinicians should screen individuals with schizophrenia for bipolar disorder, autism spectrum features, and alcohol use problems due to established genetic causal relationships. These findings support integrated care approaches and may inform genetic counseling for families with psychiatric disorders.

Sample sizes not reported. Mendelian randomization assumes genetic variants only affect outcomes through the exposure, which may not hold for complex psychiatric traits. Results apply to genetic predisposition rather than clinical diagnosis. Limited to populations of European ancestry typically used in GWAS.

ObjectiveSchizophrenia is a globally prevalent complex neuropsychiatric disorder that is frequently comorbid with various psychiatric disorders, leading to poor prognoses for affected patients. However, the causal relationships between schizophrenia and these comorbid disorders remain unclear.MethodsWe utilized Mendelian randomization to investigate the causal effects of schizophrenia on eight psychiatric disorders, including alcohol use disorder, anorexia nervosa, anxiety disorders, attention-deficit hyperactivity disorder, autism spectrum disorders, bipolar disorder, depression, and obsessive-compulsive disorder, using data from the Psychiatric Genomics Consortium and other extensive Genome-Wide Association Studies. We employed the inverse variance-weighted method as the primary analysis, complemented by Mendelian randomization-Egger, weighted median, Mendelian randomization-Presso, Steiger filtering, leave-one-out sensitivity analysis, and reverse Mendelian randomization to address potential biases and validate the directionality of the causal relationships.ResultsOur analysis revealed that a genetically predicted one-log unit increase in schizophrenia risk was associated with a 70.7% increase in the odds of bipolar disorder (odds ratio: 1.707, 95% confidence interval: 1.58-1.84). We also found strong evidence regarding a causal relationship of schizophrenia with autism spectrum disorders, showing a 17.4% higher odds (odds ratio: 1.174, 95% confidence interval: 1.11-1.24).

Additionally, schizophrenia conferred a 14.5% elevated risk of alcohol use disorder (odds ratio: 1.145, 95% confidence interval: 1.09-1.21), while a statistically significant yet clinically marginal association was observed with depression (odds ratio: 1.004, 95% confidence interval: 1.003-1.006). No causal relationships were detected between schizophrenia and attention-deficit hyperactivity disorder, anorexia nervosa, anxiety disorders, or obsessive-compulsive disorder. Sensitivity analyses reinforced these findings, and reverse Mendelian randomization analyses provided no evidence of reverse causal impacts on schizophrenia from the disorders examined.ConclusionThese findings confirm schizophrenia as a significant genetic risk factor for bipolar disorder, autism spectrum disorders, and alcohol use disorder. Our findings enhance understanding of the interrelationships among psychiatric disorders and offer novel insights into the clinical diagnosis and management of psychiatric comorbidities.