This paper is a narrative review, meaning the author gathered and discussed already published studies rather than running a new one. It looks at sleep and body-clock problems in adolescents and adults with mood disorders, mainly major depressive disorder and bipolar disorder, and draws on some studies of children too. The author argues that sleep trouble is common in these disorders and may help cause and maintain them, not just tag along with them.
The review reports figures from other studies. Insomnia symptoms are reported by a large share of people with major depression (between 60% and 84%). In one study of 553 young people with major depression, most reported sleep problems, mostly insomnia (72.7%). In a study of 4,500 12- to 17-year-olds, those who had trouble sleeping reported more use of alcohol (odds 2.6 times higher), marijuana (2.4 times), and cigarettes (2.2 times), though the review does not say who they were compared with.
The author also reviewed some treatments. In one trial, adding a sleep therapy called CBT-I to an antidepressant raised depression remission (61.5%) above a comparison psychotherapy (33.3%). The author notes that CBT-I has not yet been tested in bipolar disorder, and cautions that mood medications can affect sleep and cloud these findings.
Source: Harvey A. Sleep and Circadian Functioning: Critical Mechanisms in the Mood Disorders?. Annual Review of Clinical Psychology (2011). doi:10.1146/annurev-clinpsy-032210-104550