LAUSR

Evening chronotype is associated with greater reports of insufficient sleep and sleep-related distress. Little research has examined this relationship within the context of pregnancy. This study investigated whether eveningness predicts insomnia severity, sleep effort, dysfunctional sleep beliefs, and sleep reactivity to stress in pregnant women with insomnia disorder. Pregnant women with insomnia disorder who spoke English or Spanish enrolled in a clinical trial of cognitive behavioral therapy for insomnia (N = 178; M age = 32.6 years). Before beginning treatment, participants completed the Composite Scale of Morningness (CSM), Insomnia Severity Index (ISI), Glasgow Sleep Effort Scale (GSS), Dysfunctional Beliefs and Attitudes about Stress Scale (DBAS), and Ford Insomnia Response to Stress Test (FIRST). Participants were categorized into evening, intermediate, or morning chronotypes (bottom 25%, middle 50%, or top 25% of CSM scores, respectively). MANCOVA examined whether chronotype predicted higher baseline ISI, GSS, DBAS, and FIRST scores after adjusting for age, gestational week of pregnancy, and language. Sleep measures collectively differed by chronotype, F(8, 336) = 4.05, p < .001; Wilk’s Λ = .83, partial η-sqd = .09. Follow-up ANOVAs testing individual dependent variables were all significant (partial η-sqd = .04 – .10, p < .05). Pairwise comparisons (Bonferroni-adjusted; p < .05) found that evening types had higher ISI scores than intermediate (M difference = 2.21) and morning types (M difference = 2.30), and higher DBAS scores than morning types (M difference = .95). Morning types had lower FIRST scores than evening (M difference = 5.44) and intermediate types (M difference = 3.89). Evening chronotype was associated with greater insomnia severity and maladaptive sleep-related cognition than other chronotypes among pregnant women with insomnia disorder. Future research may examine whether differences in chronotype have implications for insomnia treatment outcome during pregnancy, and whether greater morningness confers protection against sleep challenges during the early postpartum period. NIH R01 NR013662