Gender differences in like-sex middle-aged twins: an extended network analysis of depressive symptoms, cognitive functions and leisure activities.

Background: Depression affects twice as many women as men. Risk factors for depression certainly impact this difference, but their strong interconnectedness challenges the assessment of standalone contributions. Network models allow the identification of systematic independent relationships between individual symptoms and risk factors. This study aimed to evaluate whether the extended networks of depressive symptoms, cognitive functions, and leisure activities in like-sex twins differ depending on gender or zygosity.

Methods: Twins, including 2,040 women (918 monozygotic and 1,122 dizygotic) and 1,712 men (730 monozygotic and 982 dizygotic), were selected from the Danish Twin Registry for having, along with their like-sex co-twin, completed measures of depressive symptoms, cognition, and leisure activities (physical, intellectual, and social). Network models were estimated and compared at three levels: co-twins to each other within groups defined by gender and zygosity; monozygotic to dizygotic twins within the same gender, and between genders.

Results: No significant differences were observed when co-twins were compared to each other, regardless of the pair's zygosity or gender, nor when monozygotic twins were compared to dizygotic twins within gender. However, the gendered networks differed significantly in global strength, structure, and partial correlations between specific depressive symptoms and risk factors, all indicating stronger connectedness in women relative to men.

Conclusions: Environmental factors appear to best explain between-gender network differences. Women's networks showed significantly stronger associations both among depressive symptoms and between depressive symptoms and risk factors (i.e., decreased cognition and leisure activities). Longitudinal research is needed to determine the causality and directionality of these relationships.