The Role of Sex in Clinical Characteristics and Pharmacological Treatment of Bipolar Disorder

There has been an increasing focus on sex differences in bipolar disorder in recent years, yet much remains to be understood about their impact on clinical characteristics and treatment approaches. The aim of this study is to identify sex differences that could alter diagnosis and treatment strategies, potentially improving patient compliance and outcomes. This retrospective study analysed data from interviews with 340 participants (171 men, 169 women; ages ranging from 18 to 82 years) from the BIPFAT/BIPLONG study at the specialised outpatient centre for bipolar disorder at the Medical University of Graz, Austria. We examined sex differences in clinical characteristics and drug therapy primarily using logistic and linear regression models, with chi-square tests and Mann-Whitney U tests applied as supplementary analyses for subgroup comparisons. Our findings revealed that the age of onset for bipolar disorder was earlier in women (B = -3.05, 95% CI = [-5.08, -1.02], p = .003), with women reporting their first affective symptoms at an average age of 22.7 (SD = 9.9) compared to 26.4 (SD = 12.1) in men. Comorbid obsessive-compulsive disorder was significantly more prevalent in women (OR = 2.24, 95% CI = [2.12, 41.33], p = .003). In comparison, men were shown to experience manic episodes per year more frequently (B = -.32, 95% CI = [-.59, -.05], p = .019). Differences in treatment emerged only within specific age subgroups rather than the overall study sample. Overall, we found fewer differences than expected, which suggests that factors other than sex play a greater role in the course of bipolar disorder. Our analysis indicates that more women are suffering from OCD as comorbidity than men, a topic that has not yet been extensively researched. While previous studies mostly show that men have an earlier onset of symptoms, we found the opposite in our sample. Another notable difference in illness course was that men experienced more manic episodes per year. Further research in this area is needed to verify our findings, ideally focusing specifically on OCD in bipolar men and women, as sex differences in this comorbidity remain underexplored.