Insomnia
While insomnia is a common symptom of depression, antidepressants are effective for treating sleep problems whether or not they are associated with depression. While all antidepressants help regulate sleep, some antidepressants such as amitriptyline, doxepin, mirtazapine, and trazodone can have an immediate sedative effect, and are prescribed to treat insomnia. Amitriptyline and doxepin both have antihistaminergic, anticholinergic, and antiadrenergic properties, which contribute to both their therapeutic effects and side effect profiles, while mirtazapine's side effects are primarily antihistaminergic, and trazodone's side-effects are primarily antiadrenergic. Mirtazapine is known to decrease sleep latency (i.e., the time it takes to fall asleep), promoting sleep efficiency and increasing the total amount of sleeping time in people with both depression and insomnia.
Trimipramine
In clinical studies, trimipramine has been found in doses of 50 to 200 mg/day to significantly increase sleep efficiency and total sleep time and to decrease waking time for up to 3 weeks in patients with insomnia. It also improved subjectively perceived sleep quality and well-being during daytime. Monitoring of patients upon discontinuation of trimipramine found that it did not cause rebound insomnia or worsening of sleep quality in subjective evaluations of sleep, although objective measurements found total sleep time below baseline in a subset of patients during trimipramine withdrawal.