Chapter 1 26 Box 1.1 Summary of research gaps in the current literature on depression and sleep. Oral contraceptives (OCs) Most studies on OC use and depression have used cross-sectional data or naturalistic prospective data, which increases the likelihood of healthy user bias in the sample. Furthermore, the majority of studies have excluded participants with a lifetime history of psychiatric diagnoses, meaning these current studies cannot be generalized to those with a previous or current psychiatric disorder. There are numerous studies on OC use and sleep, but most studies used retrospective setups and were limited by small sample sizes. Furthermore, the relationship between OC-associated cortisol changes and sleep have not yet been addressed. Gender-affirming hormone therapy (GAHT) The topic of depression in transgender hormone users has been studied, but most studies used clinical diagnoses or total depressive symptoms to address depressive symptoms, and further knowledge on symptom changes after GAHT use is still lacking, as is knowledge on changes in depressive symptoms after masculinizing compared to feminizing GAHT use. Numerous previous studies also used data obtained from medical files, which could be biased by participants providing socially desirable answers to their healthcare providers in order to gain or keep access to gender-affirming care. Other studies compared depressive symptom severity when participants were still waitlisted to depressive symptom severity after years of GAHT, which means that the outcomes could be confounded by a multitude of psychosocial changes. Studies on sleep and GAHT thus far are still very scarce. Secondly, we hypothesized that the use of OCs and feminizing GAHT would be associated with increases in poor sleep quality and insomnia, whereas use of masculinizing GAHT would be associated with decreases in poor sleep quality and insomnia. However, based on the existing cisgender paradox in sleep, we also hypothesized that use of feminizing GAHT would be associated with better objective sleep, including longer TST, shorter SOL, shorter WASO, longer SWS and longer REM sleep latency, and with an earlier chronotype. We also hypothesized that use of masculinizing hormones would be associated with poorer objective sleep, including shorter TST, longer SOL, longer WASO, shorter SWS and shorter REM sleep latency, as well as a later chronotype.
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