Sleep in Other Medical, Neurologic, and Psychiatric Disorders
Psychiatric comorbidity
Depression commonly causes insomnia and early awakening; bipolar disorder carries risk of mania with sleep deprivation. Anxiety disorders cause sleep-onset difficulty. PTSD causes nightmares and fragmented sleep. Treat the underlying disorder; CBT-I can be adapted.
Neurologic disease
Parkinson disease and other synucleinopathies are associated with RBD and insomnia. Stroke and neurodegenerative disease can cause sleep-disordered breathing and central apnea. Epilepsy may show seizures during sleep; sleep deprivation lowers seizure threshold.
Medical conditions and medications
Heart failure, COPD, and chronic pain disrupt sleep. Medications matter: steroids and stimulants cause insomnia; opioids cause central apnea and hypoventilation; benzodiazepines and Z-drugs cause sedation and complex behaviors; REM-suppressing antidepressants can mask narcolepsy on MSLT.
Traps
Do not attribute all insomnia to a primary sleep disorder without screening for depression. Remember that sleep deprivation can trigger mania. Consider medication effects before adding new drugs.
Rule of thumb: New insomnia in a patient starting a steroid or stimulant should prompt medication review before a new hypnotic is prescribed.