Rumination
Studies on what groups of people ruminate and how much show that women generally ruminate more than men. This difference is the biggest in teenage years, but on the whole it is small. Studies on this suggest that the higher likelihood for women to ruminate might explain the generally bigger portion of women suffering from depression compared to men. This finding is limited by similar things such as worry and neuroticism playing into the association, though. The two-factor model suggests that it is the higher rates of brooding among women specifically that is driving the gender differences we see in depressive symptoms.