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.
Psychological stress and sleep
Insomnia is a common condition affecting up to a fifth of the population in many countries across the world and is often complicated by a number of psychiatric conditions. Paradoxical insomnia is the phenomenon of a discrepancy between reported sleep duration and objective measurement of sleep. In some cases however the stress and anxiety produced by this perception does in fact result in an objective reduction in quality of sleep.