Sometimes prescription medicines used mainly to treat depression may ease insomnia when taken in lower doses. Although widely used, these are not approved by the U.S. Food and Drug Administration (FDA) for insomnia. When insomnia is related to depression or anxiety, these antidepressants may be added to treatment. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.