Hate winter? Scientists believe they've found the protein that causes winter-specific depression, a psychological condition known as seasonal affective disorder (SAD). According to study conducted by the University of Copenhagan in Denmark, people who develop SAD have less access to
serotonin, the brain signalling compound associated with feelings of well-being and happiness, as the days get shorter in the winter months. This is because their brains ramp up the production of a transporter protein called
serotonin transporter, which transports serotonin into the nerve cells where it’s not active.
Source: http://sciencealert.com.au/news/20142710-26407.html