There is definitely a connection between sleep problems—particularly insomnia—and depression. We frequently find insomnia in patients diagnosed with clinical depression; in fact, sleep disturbance is one of the core symptoms of clinical depression. However, people with insomnia are more likely to develop depressive and anxiety disorders.
People with depression often have severe sleep disturbance, and they respond more slowly to treatment than other patients with sleep disorders. They also have an increased risk of recurrence of depression, and there is some evidence that people with depression also experience suicidal thoughts.
Oversleeping is less common in cases of depression—it occurs in about 15% of patients with depression, mostly among younger adults, particularly those with bipolar affective disorder (manic depression). Excessive sleepiness can be a symptom of depression, but most patients with depression have insomnia.
Depression is often associated with disturbances in vegetative functions—the things the body does to keep itself alive, such as eating and sleeping. Depression is usually associated with loss of appetite and weight loss, but it can also result in increased appetite and weight gain.
There aren't many well-controlled studies on the effectiveness of different treatments for concurrent depression and insomnia. In general, medication treatments take four different approaches: