Higher morning NR1D1 (REV-ERBΑα) expression, robust circadian activity, and less light at night predict lower...

Depression poses a challenge in high-latitude regions. Research suggests links between light exposure, clock genes, and mental health. Understanding these connections is crucial, given light's influence on circadian rhythms and potential downstream effects on depression.

This study involved up to 64 Arctic residents per season, up to 29 of whom contributed a blood sample at 08:00 during solstices and equinoxes for determination of NR1D1 (REV-ERBα) expression by real-time PCR. Participants in each season also completed the Beck Depression Inventory II (BDI) and seven-day actigraphy.

Higher morning NR1D1 expression independently predicted lower BDI scores, controlling for season, age, and sex (β = -0.400, p = 0.001). Multiple regression, adjusted for season, showed significant associations between higher BDI scores and higher L5 (least active 5 h), lower RA (relative amplitude of motor activity), higher L5 BLE (L5 of blue light exposure), earlier activity phase, and shorter total sleep duration, among several actigraphy measures. After adjusting for sex, and age all these predictors remained significantly associated with higher depression scores. Morning NR1D1 expression was the strongest predictor of BDI scores, particularly around the spring equinox (R² = 0.358; p = 0.005).

We observed a season-dependent inverse correlation between morning NR1D1 expression and BDI scores in Arctic residents. Higher morning NR1D1 expression was associated with lower self-reported depressive symptoms, even after controlling for demographic factors. Disruptions in sleep and light hygiene during nighttime hours were also independent predictors of higher BDI scores.

The study had a modest sample size and NR1D1 expression was assessed only once in the morning.