This report describes and compares specific sleep measures in a cohort of depressed and non-depressed pregnant women. We showed that depressed women have significantly more fragmented sleep, as reflected by longer sleep latencies, longer periods of nocturnal wakefulness, and poorer sleep efficiency, during the second half of pregnancy. However, sleep deprivation, as reflected by total sleep time and symptoms of insomnia only differed between the two groups at 20 weeks gestation. It is likely that typical physiological changes that occur towards the end of pregnancy, such as increased abdominal size and physical discomfort, in addition to increasing progesterone levels [36
] account for the congruence between groups in the third trimester. However, it is worth noting that the rate of insomnia increased among the non-depressed women by 36 weeks to approximately 40% of the sample which is consistent with several reports. [6
] These disparate sleep patterns suggest that the significance of disturbed sleep among depressed pregnant women may be more important in earlier gestation. We speculate that in early gestation the interaction between depressive symptoms and disturbed sleep may have a greater impact on maternal physiology and subsequent adverse outcomes. Depression and disturbed sleep are both associated with inflammation and neuroendocrine dysregulation [38
]. Disturbances or alterations in maternal physiology, such as inflammation, anemia or high norepinephrine levels, particularly in early gestation, have been identified to increase the risk for preterm birth [42
] Further investigation is warranted to determine whether disturbed sleep is associated with adverse pregnancy outcomes via dysregulation of these biological pathways.
This is the first report, as far as we are aware, to evaluate data that contain SSRI use and sleep in pregnant women. While SSRIs are the first line of pharmacologic treatment for depression, [45
] clinicians are often hesitant to prescribe them during pregnancy and women are resistant to taking them. The medications used by these women had differential effects on sleep despite being associated with symptomatic and functional improvement. [46
] A range of SSRIs used allowed us to evaluate only the effects of this class of drugs rather than individual medication effects. It is also likely that a subset of women, within the course of treatment for depressive symptoms, experienced improvement in sleep. [28
] Further exploration indicated differential effects of depression on sleep that varied according to whether the women were taking an SSRI. These data are however, in accordance with the existing literature. SSRIs often have short-term sleep disturbing properties, but are commonly used to treat symptoms of insomnia as well as depression in women. Not all antidepressants have the same effects on sleep. [28
] Some have been shown to reduce REM sleep (tricyclics), while others alter sleep consolidation and architecture that may be relevant to clinical response (SSRIs). [29
] Future studies should explore the specific effects of SSRIs on both subjective and physiological measures of sleep in depressed as well as non-depressed pregnant women.
The literature describing and comparing sleep in depressed and non-depressed women is sparse. Our findings corroborate and extend the literature that sleep is more disturbed among depressed pregnant women. [22
] We also contribute by providing evidence that the sleep of non-depressed pregnant women becomes progressively worse across pregnancy whereas the sleep of depressed pregnant women starts poor and remains poor. Depression does not influence sleep independently. It is very likely that sociodemographic factors contribute to the dynamics of this relationship. In the current cohort, for example, depressed women delivered more children, were more likely to be at a lower SES level, and more likely unemployed. These sociodemographic characteristics are known to contribute to sleep problems and higher levels of depression. [48
] These findings merit further investigation in order to determine whether the changes in sleep are solely a result of depression and pregnancy or further exacerbated by demographic factors.
We further sought to extend the current literature on disturbed sleep and the potential for increased risk for greater depressive symptoms among those who were not depressed at 20 weeks. We found that several aspects of poor sleep are associated with higher depressive symptoms and an increased risk for developing MDD, which corroborate the existing literature. [18
] Women who become depressed took twice as long to fall asleep, spent twice as much time awake, and had worse sleep efficiency than women who did not become depressed. Interestingly, we found that among the women who were not depressed at 20 weeks gestation, those who napped for more than 30 minutes per day were at an 8-fold risk for developing MDD by week 30. This is consistent with data from Wolfson et al [27
]who found that longer nap times in late pregnancy were associated with higher depressive symptoms in the postpartum.
This is only the second study to evaluate sleep in pregnant women who were clinically diagnosed with depression and the first to have three time assessments across pregnancy. Field and colleagues [22
] evaluated 253 women at approximately 22 and 32 weeks gestation and found greater sleep disturbances determined by visual analogue scales among the depressed women. This is also the first study to utilize interview-assessed sleep information collected by a clinician. Previous studies have relied on self-report questionnaires such as the Pittsburgh Sleep Quality Index (PSQI) [24
] or visual analogue scales. [22
] While not the gold standard for measuring sleep, the SIGH-ADS [32
] allows for a more detailed and quantitative account of the various sleep parameters known to be associated with depression, including sleep onset latency, wake after sleep onset and symptoms of insomnia. [18
] Furthermore, while the PSQI has good validity in depressed and/or pregnant populations, [24
] the recall period is over the previous 30 days. The SIGH-ADS, [32
] on the other hand, asks about the previous 7 days. This period of recall is considered more reliable. Ideally, sleep diaries would be used in order to capture the daily variability in sleep across a longer time period in conjunction with objective sleep measures, such as actigraphy or polysomnography.
The current findings support the growing evidence that depressed women have more sleep disturbances than non-depressed women. [22
] While this study has several positive attributes, including a large community-dwelling cohort that was followed prospectively across pregnancy and the use of “gold standard” tools for clinical diagnosis of depression, there are some limitations. First, sleep data were based on retrospective recall only. While this is a common data collection method, data collected in a prospective manner, such as with sleep diaries, would assist and confirm the participant reports. The interpretations and associations with future depressive symptoms would also be enhanced with prospective assessments of sleep. We also did not have a sleep quality question available. Since sleep disturbance is both a physiological as well as psychological stressor, it would have been useful to describe and compare the quality of these women’s sleep. Finally, pre-pregnancy sleep or sleep during the first trimester would have further allowed for a more careful longitudinal examination of sleep disturbances across the whole gestational period.
Nonetheless, the data have important clinical implications. We show that specific components of sleep are distinctly more disturbed in depressed pregnant women compared to non-depressed pregnant women. Pregnant women who are depressed or have a history of depression are more vulnerable to adverse pregnant outcomes. [55
] Hence, evaluating and screening for sleep problems during pregnancy in conjunction with treating depression could augment the prevention and/or amelioration of the current, as well as future, depressive episode. These findings are particularly important given the elevated risk for future depressive episodes among individuals who have sleep problems. [19