Doctors often prescribe antidepressants to treat insomnia. Antidepressants have a history of producing positive results with those affected by insomnia. They can be used long term. Antidepressants are not habit forming, and so offer a relatively safe form of medication. Antidepressants are normally given when anxiety or depression are recognized as root causes for insomnia. However, there is very little evidence to substantiate the use of antidepressants to treat insomnia in non-depressed patients (Sharpley AL, Cowen PJ. Effect of pharmacologic treatments on the sleep of depressed patients. Biol Psychiatry 1995;37:85-98).

Antidepressants have a range of adverse effects including anti-cholinergic effects, cardiac toxicity, orthostatic hypotension and sexual dysfunction (selective serotonin reuptake inhibitors [SSRIs]). Tricyclic antidepressants and SSRIs can exacerbate restless legs syndrome and periodic limb movement disorder in some patients. The lethal dosage/effective dosage ratio for tricyclic antidepressants is smaller than that for benzodiazepines (Walsh JK, Erman M, Erwin CW, Jamieson A, Mahowald M, Regestein Q, et al. Subjective hypnotic efficacy of trazodone and zolpidem in DSMIII-R primary insomnia. Human Psychopharmacology 1998;13:191-8)