Question: Do people’s moods actually vary with the seasons? If so, in what ways and what are some of the reasons behind this phenomenon?
Answer: While findings regarding changes in mood states across the seasons in samples of healthy people are mixed, there is strong evidence for a subtype of mood disorder that is seasonal in nature. Seasonal Affective Disorder (SAD) is a mood disorder characterized by seasonal cycles, most typically emerging during the short and cold days of winter in more northern latitudes and remitting in spring as the days become longer.
It is currently estimated that half a million people in the U.S. suffer with the much more common winter depression form of SAD, with higher rates the more northern the latitude. Symptoms of winter depression include changes in appetite—with a craving for carbohydrates specifically—weight gain, energy loss, fatigue, hypersomnia, concentration difficulties, irritability and social withdrawal (DSM-IV; APA 1994). These symptoms must be accompanied by impairment in social, occupational or other domains of function to merit a diagnosis.
The good news is that randomized, controlled trials have shown that light therapy (LT) administered in patients’ homes for as little as 90 minutes per day produces marked improvement in mood and related somatic symptoms. One recent study suggests that cognitive-behavioral therapy, which focuses on modifying basic assumptions and beliefs to help control aberrant emotional experiences, when used in conjunction with LT produces even larger improvements in mood in patients with the disorder than LT alone (see Rohan et al., 2007; Journal of Consulting and Clinical Psychology, 75; 489-500).
Pharmacotherapy, typically consisting of medications that enhance the action of the neurotransmitter serotonin in the brain by slowing down deactivation after release, have also shown efficacy for treatment of SAD. Findings regarding pathogenesis have been mixed, pointing to an array of genetic, neurotransmitter and circadian-cycle risk factors.