Seasonal Affective Disorder: A Narrative Review

This narrative review of research includes summaries of 46 papers on seasonal affective disorder that were published during the period 2019-2023. The publications are primarily cross-sectional studies of risk factors, randomized controlled trials for light therapy and cognitive behavioral therapy and systematic reviews. A few of the papers are focused on the prevalence of seasonal affective disorder which has varied by latitudes and climates from 3% in Saudi Arabia to 21% in Norway, suggesting length of day and sunlight effects. Only a few studies focused on the negative effects of seasonal affective disorder including sleep problems, depression and poor performance on memory tasks. Most of the research has addressed risk factors for developing seasonal affective disorder including younger age, female gender, dependent personality, seasonal beliefs, chronotype (eveningness), inactivity, insomnia and depression. Very few potential underlying mechanism studies appeared in this literature with the exception of MRI studies suggesting reduced brainstem volume. In contrast, many intervention studies were published recently including light therapy and cognitive behavioral therapy. Methodological problems relate to the variability in the assessments of seasonal affective disorder, the reliance on self-report measures and the cross-sectional data that are not definitive about directionality of predictors and effects of seasonal affective disorder.