Some people suffer from 'winter blues' while others have no issue.
Seasonal Affective Disorder (SAD)
affects people as daylight levels drop in autumn. At Northern European latitudes (for example all of Scandinavia, Glasgow and Moscow) around 1 person in 6 suffers from SAD.
Psychologists have searched for reasons why. A small longitudinal study concluded that people with Seasonal Affective Disorder show significant seasonal differences in the way they regulate the neurotransmitter