Scientist Identified Reason for Seasonal Depression

Winter: we have all had all those moments when we would instead stay in bed than head out into the cold, dark day. But for all those with seasonal affective disorder, winter can lead to a serious form of depression. In a new research, scientists claim to have recognized what leads to the condition.

Lead investigator Brenda McMahon and her co-workers, recently presented their outcomes at the European College of Neuropsychopharmacology (ECNP) Congress in Berlin, Germany.

Seasonal affective disorder (SAD) is a type of depression that is likely to happen at the same time every year, from autumn through winter. SAD impacts about 500,000 individuals in the US, while 10-20% of People in America suffer from the “winter blues” – a less severe form of seasonal depression.

Signs of SAD are identical to those of clinical depression and consist of stress, sadness, irritability, social withdrawal, lack of focus and fatigue.

The actual cause of SAD is uncertain, but past research have showed that it is activated by a decrease in sunlight in autumn and winter months. Experts have hypothesized that the decreased visibility to light can lead to instability of brain chemicals known as neurotransmitters, which affect mood.

In this recent study, the team develops on this theory and states they have proved the biochemical cause of SAD.

Finding ‘the dial the brain turns up’ to modify to modifying seasons

To achieve their results, McMahon and her team used position emission tomography (PET) to scan the brains of 11 individuals with SAD and 23 individuals without the disorder.

In specific, they evaluated individuals’ levels of the serotonin transporter (SERT) protein in both winter and summer season. SERT is accountable for the travel of serotonin – a neurotransmitter identified to regulate mood.

Outcomes of the analysis exposed that in winter, SERT levels in individuals with SAD were 5% greater than in summer, while individuals without the condition revealed no change in SERT levels. The greater levels of serotonin in the winter suggest a greater elimination of serotonin from the brain, which can result in depressive symptoms.

“SERT provides serotonin back into the nerve cells where it is not active, so the greater the SERT activity, the decrease the activity of serotonin,” describes McMahon. “Sunshine keeps this setting normally low, but when the nights develop longer while in the autumn, the SERT levels increase, resulting in reducing active serotonin levels.”

“Many people are not actually affected by SAD,” she continues, “and we have identified that these individuals don’t have this increase in SERT activity, so their active serotonin levels stay high during the winter.”

McMahon claims she considers the team has “identified the dial the brain turns up when it has to modify serotonin to the changing seasons.”

Leaving comments on these results, Prof. Siegfried Kasper, of the ECNP, says:

“SERT fluctuations related with SAD have been seen in past research, but this is the initial research to follow sufferers through summer and winter. It seems to offer verification that SERT is related with SAD.”