Claims of sex-dependent effects in the behavioral and brain sciences are infrequently supported by valid statistical comparisons.

Interest in precision medicine has accelerated efforts to identify sex-dependent responses to treatments and interventions. Those efforts have, both historically and today, been concentrated in fields related to the brain and behavior. Here, we show that even though articles claiming sex-dependent effects are far more prevalent in the neurosciences than in other fields, those claims are infrequently supported by appropriate statistical evidence. Of 200 recent articles in the behavioral and brain sciences with a claim of a sex- or gender-dependent effect in the title, only 24% supported the claim with appropriate evidence-that is, they compared the effect statistically across sex and reported results consistent with the claim. In 9%, an appropriate test was described but the results were incomplete or missing; another 9% contained results that directly contradicted the claim. In most articles (58%), the effect was not compared statistically across sex. Across six brain-related research areas (behavioral sciences, clinical neurology, neurosciences, psychiatry, psychology, and substance abuse), neurosciences had the lowest rate of appropriate evidence (18%) and psychology the highest (39%). Studies on nonhuman animals supported the claim significantly less frequently (15%) than studies on human participants (34%;