General discussion 259 symptoms if they also reported hot flashes. In Chapter 6 we used ambulatory sleep EEG measurements to assess possible changes in sleep architecture before and after 3 months of GAHT use. Results indicate that after 3 months of masculinizing GAHT, participants had shorter SWS durations, shorter REM sleep latencies, and longer REM sleep durations. After 3 months of feminizing GAHT, participants showed no significant changes in sleep architecture. In Chapter 7, we examined whether preferred sleep timing changed after 3 months of GAHT. After 3 months of masculinizing GAHT, participants reported a later midpoint of sleep, while after 3 months of feminizing GAHT, participants reported an earlier midpoint of sleep, in line with chronotype differences in the cisgender population. 1.3 Sex hormones, and associations between depression and sleep In our systematic review in Chapter 8, findings reveal that both in depressed participants and healthy controls, poor sleep is associated with depression or negative mood. This was different in participants with premenstrual dysphoric disorder (PMDD) or participants on sex hormone interventions: in these samples, the associations between sleep and mood symptoms were less clear. In Chapter 2, in which we examined differences in depression and insomnia between OC users and non-users, we showed that a current or previous diagnosis of depression did not increase the risk of OC use and insomnia symptoms. Likewise, comparing the findings on GAHT in Chapter 3 with those in Chapter 5, 6 and 7, we do not find adverse changes in sleep and corresponding increases in depressive symptoms. Results from our factor analysis in depressive symptoms indicate that in transgender people starting GAHT, insomnia symptoms do not show strong correlations with other depressive symptoms. We also find that use of masculinizing GAHT is Research question 3: What are the effects of sex hormones on the association between depression and sleep?
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