Chapter 8 240 between testosterone, sleep and depression are scarce. An important note in the findings of Kische et al. is that their participants’ age range was partially outside of the set age range in this review. Although they corrected for age in their analyses, in the interpretation of their results it should be noted that the results also contain postmenopausal women and older men, who both have lower endogenous hormone levels than their younger counterparts (Freeman et al., 2004; Muller et al., 2003). Studies with both pre-and post-measurements in healthy women starting hormonal interventions (such as oral contraceptives) are very underrepresented in this field. Our initial full search did find three studies on sleep and depression in users and non-users of oral contraceptives. However, these studies were cross-sectional, and included long-time oral contraceptive users, whose oral contraceptives did not represent a hormonal intervention. Thus, we decided not to include these studies for this review. An important consideration in some of the studies, especially the hormone suppression study by Ben Dor et al., is that hormones can also affect physical state. A well-known factor around menopause is that women can experience hot flashes, presumably due to drops in endogenous estrogen and progesterone, which at night can also affect sleep quality and nocturnal awakenings (Joffe et al., 2013). Indeed, Ben Dor et al. reported an increase in hot flashes in their participants after suppression of sex hormones. OC might have also side effects such as lower libido and weight gain, both of which can affect users’ quality of life. Additionally, both lower libido and weight gain can be symptoms of depression in validated depression questionnaires, and as a consequence oral contraceptive side effects might also cause depression scale scores to increase. Altogether, the physical effects of sex hormone changes can also affect sleep and depression indirectly. 4.3. Implications Estrogen has been associated with sleep, which may be relevant for clinical purposes. Sex hormone levels were not clearly associated with depressive symptoms nor a diagnosis of depression. It is possible that not the absolute sex hormone levels, but relative changes in sex hormone levels are related to mood changes (Bloch et al., 2003). For example, a relative reduction in
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