Sleep results from changes in the balance of major neurotransmitters in the brain, such as serotonin, norepinephrine, dopamine, melatonin and others. Many of these systems are also responsible for multiple brain functions, including those related to mood and other cognitive/emotional behaviors. So it is not surprising that significant interactions occur between sleep and depression and/or depressed mood. Similarly, studies clearly demonstrate that a reliable nigh of sleep is correlated with a positive mood or even improves mood in healthy people. Undoubtedly, since sleep and mood are intricately related, everyone should evaluate their sleep/wake patterns when they are feeling irritable, moody and/or sad.
Studies link persistent insomnia (difficulty falling asleep and/or maintaining sleep_ with depressed mood and the onset of major depression. In a 1996 study of adult men and women, Breslau and colleagues concluded that nightly insomnia and other sleep disturbances for two weeks or more were a risk factor for future episodes of depression. In 1998 and 2003 studies, my colleagues and I found that inadequate and irregular sleep/wake schedules are also associated with depressed mood in adolescents and also for women during pregnancy and the postpartum months.
Studies estimate that often sleep problems such as insomnia, insufficient sleep and poor sleep quality exist in 50-90% of people with depression. Twenty percent of those who complain of insomnia show signs of depression (Tsuno and colleagues, 2005). It’s also striking that sleep disturbance is one of the key predictors of an episode of depression (Riemann and colleagues, 2001). In a 2005 study, Ross and colleagues discuss how symptoms of insomnia are tied to significant risk of depression and anxiety problems. Sleep disturbances are often described as symptoms of a variety of emotional difficulties, and treating sleep problems, improving sleep quality/quantity, often has a positive impact on mood.
Understanding Sleep, Sleep Health Including Sleep Disorders and Sleep Aids