Research suggests a bidirectional association between sleep disturbances and posttraumatic stress disorder (PTSD) symptoms. However, most studies have been conducted with group-level data, which do not necessarily capture the associations between PTSD symptoms and sleep within an individual over time. This study aimed to add to the literature concerning the association between sleep and PTSD and extend these findings to investigate the effect of sleep disturbances on positive affect. Ecological momentary assessment (EMA) was used to examine the daily temporal dynamics of sleep disturbances (i.e., self-reported difficulty initiating and maintaining sleep, disturbing dreams) and PTSD symptoms over 14 days in a sample of 41 trauma-exposed individuals. Multilevel models were employed to disambiguate within-person effects (i.e., intraindividual variability) from between-person effects (i.e., interindividual variability). Difficulty sleeping predicted increased PTSD symptoms at both the within-person, β = .11, and between-person levels, β = .38, as did disturbing dreams, within: β = .14, between: β = .31. Participants with higher PTSD symptom levels were likely to report increased difficulty sleeping at night, β = .40. Positive affect was unrelated to sleep at the within-person level but increased average sleep difficulty predicted lower positive affect at the between-person level. The findings indicate that sleep difficulties must be considerably more substantial than usual to affect PTSD symptoms in a noticeable way.
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