September 26, 2008 – Canadian researchers have discovered how our brains react to seasonal changes, causing seasonal depression in some people in the fall and winter.
According to the results, the activity of enzymes responsible for eliminating serotonin – monoamine oxidase – is greatly increased when the brightness decreases, and decreased when the light increases.
This is why the brain levels of serotonin – a hormone that plays a key role in neurological functions – vary according to the seasons, or more precisely according to the photoperiod (relative length of day and night).
The researchers observed that in the fall and winter, the levels of serotonin transporting enzymes are higher than in the spring, which would explain the incidence of cases of seasonal depression when the hours of sunshine decrease.
For the purposes of this study, 88 healthy adults were subjected to brain imaging examinations (CT or tomography) at various times of the year to measure the levels of monoamine oxidase.
Light: an antidepressant?
According to researcher Gilles Vandewalle, a specialist in the effect of light on mood, this discovery indicates that light could act like some of the most effective antidepressants: selective serotonin reuptake inhibitors (especially Prozac®).
In Nordic countries such as Canada, seasonal depression is estimated to affect 3% to 8% of the adult population. Light therapy is the best documented treatment for this condition. According to Gilles Vandewalle, also a doctor in neuroscience, light therapy is effective in around two out of three patients suffering from seasonal depression. Symptoms are reduced by 50% to 80%, which would be comparable to the clinical effect of antidepressants.
Pierre Lefrançois – PasseportSanté.net
According to the Globe and Mail.
1. Praschak-Rieder N, Willeit M, et al. Seasonal variation in human brain serotonin transporter binding, Arch Gen Psychiatry. 2008 Sep; 65 (9): 1072-8.