Approximately 5.1% of the cohort reported having a medical diagnosis of mood or anxiety disorder. Overall, women with a positive history of a psychiatric disorder were more likely than others to report short sleep durations, vital exhaustion and elevated perceived stress. The odds of these complaints were particularly elevated among overweight/obese women.
Substantial studies, generally conducted in men and non-pregnant women
[11–13, 15, 17] or children
[14, 16] have examined one or more aspects of the mood or anxiety disorder-sleep comorbidity spectrum agree on our conclusion. Overall, our observations of higher odds of reported short sleep duration, excessive daytime fatigue, vital exhaustion and stress in pregnant women with a history of mood and anxiety disorder are consistent with previous studies. Our results are also largely consistent with reports from earlier studies that have documented increased prevalence of sleep disorders, stress or fatigue among pregnant women with mood or anxiety disorders
[23–25, 27, 28]. A summary of findings from prior studies are presented in Additional file
1 (Table). For instance, our observation of positive associations of short sleep duration with mood or anxiety disorder is consistent with reports from Field et al.
 who evaluated the effect of depression on self-report measures of sleep disturbance among 253 pregnant women at approximately 22 and 32 weeks gestation. The authors noted that those who were classified as depressed (using Structured Clinical Interview for DSM-IV (SCID)) were more likely to report sleep disturbances compared with non-depressed ones. Field et al.
, later in a larger study among 911 pregnant women who were predominantly from low and medium socioeconomic status, replicated the same finding. In both studies the psychiatric diagnoses were made by research associates who used the SCID diagnostic instrument and who were supervised by a clinical psychologist. Okun et al.
 in their secondary data analyses study, compared sleep disturbances in depressed (N=59) and non-depressed (N=181) pregnant women. Depression was ascertained using the SCID instrument at 20 weeks of gestation and sleep variables were extracted from the Structured Interview Guide for the Hamilton Depression Rating Scale with Atypical Depression Supplement (SIGH-ADS) at 20, 30, and 36 weeks gestation. The authors found that depressed women had more fragmented sleep at each assessment (p values<0.05). However, sleep deprivation, as reflected by percentage of total sleep duration <7 hrs (39.0% vs. 21.5%, p=0.008) and insomnia symptoms (55.9% vs. 30.4%, p=0.0004), was greater for depressed women only at 20 weeks gestation compared with non-depressed ones. Given that the sleep variables used in this study were imbedded within the SIGH-ADS depression screening scale, and thus were considered in making the psychiatric diagnosis, it is difficult to discern if observed correlations are independent of intrinsic measures of depression.
Overall, findings from the earlier studies provide some objective evidence on the relation between mood or anxiety disorders and sleep disturbances. However, methodological limitations including not controlling for confounding factors, small sample size, and lack of clinical diagnosis of mood/anxiety disorders did not allow one to draw firm conclusions to be made. Overcoming some of the noted methodological limitations of prior studies, our study adds to the body of evidence evaluating the impact of a clinically-diagnosed mood or anxiety disorders on sleep during early pregnancy. However, our results and those of others
[23–25, 27, 28] are inconsistent with a report by Skouteris et al.
. Their results showed that depressive symptoms earlier in pregnancy did not impact sleep quality at a later stage in pregnancy.
Our observation of higher perceived stress score in women with mood/anxiety disorders are in agreement with previous literature
. Salacz and his colleagues found high Beck Depression Inventory (BDI) and State-Trait Anxiety Inventory (STAI) scores were associated with high levels of perceived stress (PSS score) in pregnancy women. A multiple regression analysis revealed that subjective feelings of stress explained over 50% of the variation in BDI and STAI scores
Investigators speculated that common underlying pathophysiological neuroendocrine alterations involving the hypothalamus, serotonin and melatonin synthesis and secretion may, in part, explain consistent observations of increased risks of sleep disturbance in patients with mood and anxiety disorders. This hypothesis is supported by results from clinical
[26, 33–35] and functional neuroendocrine imaging studies
[36, 37]. Investigators have documented plasma melatonin circadian rhythm disturbances during pregnancy and postpartum in depressed women and women with personal or family histories of depression
. Moreover, investigators have reported lower plasma melatonin concentrations in patients with insomnia
. Melatonin is known to play a role in the biological regulation of circadian rhythms and sleep. Both animal and human studies demonstrated agomelatine (a melatonin analogue drug acting as melatonin agonist and 5-HT antagonist) to be an effective treatment for depression and bipolar disorder
[34, 35]. Serotonin secreted from the dorsal raphe nuclei is implicated in both the control of mood and anxiety disorder pathogenesis and sleep cycles
. The suprachiasmatic nucleus of the hypothalamus regulates the release of serotonin, supporting the thesis that the hypothalamus likely plays an important role in both the control of mood and sleep-regulating systems. Increased hypothalamic-pituitary-adrenal (HPA) activity, a robust pathophysiological biomarker associated with mood/anxiety disorders
, is regarded as one important mechanism for observed associations between maternal psychiatric illness and perceived stress level
Several limitations of our study merit discussion and consideration. First, the prevalence of mood/anxiety disorder of 5.1% in this sample is well below the national prevalence estimate reported by other investigators
[21, 22]. As a result, it is likely that a considerable number of women with psychiatric illnesses were misclassified as not having mood or anxiety disorder in our cohort. This under-ascertainment of psychiatric illnesses would generally serve to underestimate the true magnitude of associations detected in our study. Second, we did not collect information on onset of psychiatric symptoms, nor did we collection on the precise date of diagnosis. We were, however, able to distinguish women who had a recent diagnosis made prior to the study pregnancy or during the first 20 weeks of the index. We did not collect information of the effectiveness of the treatment. Third, maternal habitual sleep duration during pregnancy was obtained from self-report, and thus is likely susceptible to misclassification. Reported sleep duration is known to be only moderately correlated with wrist actigraph-measured sleep duration (r=0.47), and reports are generally longer by approximately 34 minutes for each hour of objectively measured sleep duration
. Future studies will require making objective assessments of maternal sleep duration. Fourth, we did not have information concerning participants’ shift-work or insomnia status and thus cannot attribute observed associations of short sleep duration with psychiatric disorders to occupational or medical conditions associated with short sleep duration. For instance, though related, short sleep duration and insomnia are different entities. Insomnia entails dissatisfaction with the quality of sleep and an inability to sleep given adequate opportunity. Insomnia can result in short sleep duration, but individuals with short sleep duration do not necessarily suffer from insomnia (i.e., participants may sleep less because they choose to do so or because they lack the opportunity to sleep). Future studies that allow for the comprehensive ascertainment of maternal sleep disorders (e.g., sleep disordered breathing, restless legs syndrome, insomnia, and circadian rhythm disorders) will be needed to more thoroughly assess the co-morbidity of psychiatric illnesses and sleep disorders among pregnant women. Fifth, although we adjusted for several potential confounders, we cannot exclude the possibility of residual confounding due to misclassification of adjusted variables (e.g., maternal pre-pregnancy body mass index) or confounding by other unmeasured variables (e.g., maternal exposure to the shift work during pregnancy). In consideration of evidence suggesting that adiposity may be associated with both psychiatric illnesses and sleep disorders
, we report results from models which allow for assessing the independent and joint effects of psychiatric diagnoses and overweight status on each sleep complaint variable. The amount of sleep has declined by 1.5 hours over the past century, accompanied by an important increase in obesity
. Lastly, the generalizability of our study may also be limited as our cohort was primarily comprised of Non-Hispanic White and well-educated women. The concordance of our results with those from other studies that have included racially, ethnically and geographically diverse populations
[23–25, 27, 28], however, serve to attenuate these concerns.