As many as 60 million Americans — 30 percent of American men and 40 percent of American women — experience periods of insomnia [source: NINDS]. There are a handful of FDA-approved prescription medications to treat the problem, including a few types of benzodiazepines (such as diazepam), a few types of non-benzodiazepines (including Ambien and two other sleeping aids), one selective-melatonin receptor agonist (ramelteon) and one selective dual orexin receptor antagonist (suvorexant). But one of the most popular treatments for insomnia isn't FDA approved.
Twenty-one percent of all prescriptions written in the U.S. are considered to be for off-label uses, and leading the pack of those off-label drugs are antidepressants prescribed to treat insomnia [source: Nova Southeastern University]. When sleep problems arise from anxiety or depression disorders, low doses of certain antidepressants, such as amitriptyline (Elavil), mirtazapine (Remeron) and trazodone (Oleptro), may effectively treat both the symptoms of the mood disorder and the related insomnia.
Some antidepressants, such as amitriptyline, have a sedative effect because they block the reuptake (the absorption) of serotonin and norepinephrine, two neurotransmitters associated with our sleep-wake cycle. Other antidepressants also block histamine receptors; mirtazapine, for example, blocks the H1 receptor, which is why it makes you feel sleepy, and depending on dosage, also blocks the 5-HT2A and the alpha-2 adrenergic receptors.