The effect of comorbid psychiatric and medical illnesses on sleep disorder treatment.

Psychiatric, neurologic, and medical conditions frequently coexist with sleep disorders and contribute to poor treatment outcomes when unrecognized and untreated. For patients who present with excessive daytime sleepiness (EDS) or fatigue, clinicians should screen for sleep disorders (eg, obstructive sleep apnea, narcolepsy), medical and neurologic conditions (eg, cancer, Parkinson's disease), and psychiatric disorders (eg, depression, substance abuse) to determine if they are the cause or a contributing factor to sleep symptoms. Once recognized, comorbid conditions may be targeted along with EDS or fatigue using behavioral and pharmacologic treatment strategies.