The essential feature of hypersomnia related to another mental disorder is a complaint of excessive sleepiness, with either prolonged nocturnal sleep or frequent daytime sleep episodes, that has lasted for at least 1 month. These patients currently meet the criteria for another Axis I or Axis II disorder, but the sleep complaint is sufficient to warrant independent clinical attention or is atypical for the type of psychiatric disorder. The complaint must not be related to medications or another medical disorder. Mood disorders and personality disorders constitute the most frequent diagnoses in such cases.

Patients with hypersomnia in the setting of another mental disorder typically have less evidence of physiological sleepiness than patients with other hypersomnia conditions (Billiard et al. 1994; Nofzinger et al. 1991; Zorick et al. 1982). Clinicians must always consider other possible sources of hypersomnia in patients with psychiatric disorders. In particular, inadequate duration of night sleep, breathing-related sleep disorder, and narcolepsy must always enter the differential diagnosis.

Behavioral treatment No study of behavioral interventions for hypersomnia related to another mental disorder has been done. To minimize this symptom, it may be useful to maintain regular sleep-wake habits, ensure adequate bright-light exposure, and schedule competing social and physical activities, especially when sleepiness is most severe.

Pharmacological treatment As in the case of insomnia related to another mental disorder, no treatment trials have focused specifically on the diagnosis of hypersomnia related to another mental disorder. Rather, the patient’s sleep symptoms have been charted as a function of their treatment for the underlying psychiatric disorder, such as depression. For example, the profound inertia and hypersomnia often found in “atypical depression” responds along with other symptoms to MAOIs.

A complaint of hypersomnia will often influence the clinician’s decision regarding selection of particular medications. For instance, the clinician would probably not prescribe a sedating TCA for a depressed patient who reports hypersomnia. More reasonable choices might include an alerting SSRI, bupropion, or a less sedating tricyclic agent, such as desipramine or nortriptyline. The clinician also must be cautious of medications such as carbamazepine and lithium, which are often prescribed in divided doses and can increase daytime sedation. Again, “loading” the dose at bedtime can improve troublesome sedation for some patients. Antipsychotic medications and benzodiazepines, used either as primary agents or as adjuncts in the treatment of depression or mania, can also exacerbate daytime sleepiness.

Stimulant medications have been used to treat medically ill depressed patients and as treatment adjuncts in refractory or anergic/hypersomnic depression. Although these drugs have limited utility in the treatment of most mood disorders, their role in treating hypersomnia associated with depression has not been carefully evaluated in controlled clinical trials. Combinations of fluoxetine with pemoline, or an MAOI with pemoline or amphetamine, have been reported to be effective for refractory depression characterized by hypersomnia (Fawcett et al. 1991; Metz and Shader 1991). The role of modafinil in patients with hypersomnia and psychiatric disorders remains to be defined.