Hypersomnia associated with a mental disorder

**Definition:** Hypersomnia associated with a mental disorder is characterised by excessive nocturnal sleep, daytime sleepiness, or excessive napping that is sufficiently severe to constitute an independent focus of clinical attention. This is most typical of depressive disorders or the depressed phase of bipolar disorders. Patients often feel that their sleep is of poor quality and nonrestorative and may be intensely focused on their hypersomnolence. Objective evidence of excessive sleepiness on MSLT is often absent.

Note: A definitive diagnosis requires use of polysomnography and multiple sleep latency test (MSLT) to rule out other hypersomnolence disorders or other sleep disorders (e.g. obstructive sleep apnea) which might better explain the sleepiness.