Hypersomnolence has been considered a prominent feature of seasonal affective disorder (SAD) despite mixed research findings. In the largest multi-season study conducted to date, we aimed to clarify the nature and extent of hypersomnolence in SAD using multiple measurements during winter depressive episodes and summer remission.

Sleep measurements assessed in individuals with SAD and nonseasonal, never-depressed controls included actigraphy, daily sleep diaries, retrospective self-report questionnaires, and self-reported hypersomnia assessed via clinical interviews. To characterize hypersomnolence in SAD we (1) compared sleep between diagnostic groups and seasons, (2) examined correlates of self-reported hypersomnia in SAD, and (3) assessed agreement between commonly used measurement modalities.

In winter compared to summer, individuals with SAD (n = 64) reported sleeping 72 min longer based on clinical interviews (p < 0.001) and 23 min longer based on actigraphy (p = 0.011). Controls (n = 80) did not differ across seasons. There were no seasonal or group differences on total sleep time when assessed by sleep diaries or retrospective self-reports (p's > 0.05). Endorsement of winter hypersomnia in SAD participants was predicted by greater fatigue, total sleep time, time in bed, naps, and later sleep midpoints (p's < 0.05).

Despite a winter increase in total sleep time and year-round elevated daytime sleepiness, the average total sleep time (7 h) suggest hypersomnolence is a poor characterization of SAD. Importantly, self-reported hypersomnia captures multiple sleep disruptions, not solely lengthened sleep duration. We recommend using a multimodal assessment of hypersomnolence in mood disorders prior to sleep intervention.

Prevalence rates of sleep difficulties in advanced cancer patients have varied widely across studies (12 to 96%), and none of these employed a diagnostic interview to distinguish different types of sleep–wake disorders. Moreover, very limited information is available on subjective and objective sleep parameters in this population. Our study was conducted in palliative cancer patients and aimed to assess rates of sleep–wake disorders and subsyndromal symptoms and to document subjective and objective sleep–wake parameters across various types of sleep–wake difficulties.

The sample was composed of 51 community-dwelling cancer patients receiving palliative care and having an Eastern Cooperative Oncology Group score of 2 or 3. Relevant sections of the Duke Interview for Sleep Disorders were administered over the phone. An actigraphic recording and a daily sleep diary were completed for 7 consecutive days.

Overall, 68.6% of the sample had at least one type of sleep–wake difficulty (disorder or symptoms): 31.4% had insomnia and 29.4% had hypersomnolence as their main sleep–wake problem. Participants with insomnia as their main sleep difficulty had greater disruptions of subjective sleep parameters, while objectively-assessed sleep was more disrupted in patients with hypersomnolence comorbid with another sleep–wake difficulty.

The high rates of sleep–wake difficulties found in this study indicate a need to screen more systematically for sleep–wake disorders, including insomnia and hypersomnolence, in both palliative care research and clinical practice, and to develop effective nonpharmacological interventions specifically adapted to this population.