Changing with the seasons: does vitamin D affect mood?

Seasonality is defined as a change in mood and behavior with the seasons. Research shows there is a possible connection between vitamin D levels and mood (Murphy & Wagner, 2008; Lansdowne & Provost, 1998). Given that vitamin D is produced when skin is exposed to sunlight and varies with sun exposure (Bertone-Johnson, 2009), the present study examined the relationships among vitamin D levels, season, and seasonality. Vitamin D levels were expected to be relatively 1) higher, but decreasing in fall; 2) lower, but stable in winter; and 3) higher, but increasing in spring. Further, it was hypothesized that these patterns would be stronger among participants with self-reported seasonality. College women (n=187) ages 18-25 (26.7% White/Caucasian) were recruited either in fall (n=82), winter (n=34), or spring (n=62) term. Participants’ vitamin D levels were measured from their blood samples collected at baseline (T1) and again 5 weeks later (T5). Participants reported their seasonality symptoms across their lifespan using the Seasonal Pattern Assessment Questionnaire (SPAQ) at T5, and were grouped into two categories based on their SPAQ scores: at least moderate seasonality (n=88) and mild to no seasonality (n=94). Repeated measures ANOVA was used to examine mean level and change in vitamin D (from T1 to T5) for individuals in the two seasonality groups, and whether any differences depended on season of recruitment. Overall, vitamin D levels showed the expected patterns by season, but not by self-reported seasonality. That is, contrary to the hypothesis, individuals with at least moderate seasonality did not show significantly more pronounced seasonal changes in vitamin D in comparison to others. However, non-significant trends emerged, indicating the need to examine these relationships further. Future research will address study limitations by following a larger sample of participants throughout the entire year, assessing their vitamin D levels and current mood states at each season