One of the hallmark characteristics of seasonal mood disorders is poor sleep quality, due to decreases in serotonin levels and disruptions in melatonin levels. (mindbodygreen.com)
For example, reduced exposure to natural sunlight during the shorter days of winter is one big factor contributing to seasonal mood swings and winter blues. (jenniferweinbergmd.com)
This phenomenon has been researched and has shown that seasonal mood changes are real. (tools2tiaras.com)