The answer is "if they had lower than normal serotonin turnover".
Serotonin goes about as a neurotransmitter, a kind of substance that helps transfer signals starting with one territory of the cerebrum then onto the next. Serotonin impacts all aspects of your body, from your feelings to your engine abilities. Serotonin is viewed as a characteristic state of mind stabilizer. The substance assists with dozing, eating, and processing.