Medical illness. Head injuries, hyperthyroidism, asthma, hypertension, coronary artery disease, arthritis, fibromyalgia, headache and low back pain, seizures, Parkinson's disease and Alzheimer's disease, kidney disease and thyroid dysfunction, among others.
Psychiatric illness. Major depression, generalized anxiety disorder, post-traumatic stress disorder, bipolar disorder, dementia and schizophrenia, among others.
Medication and drugs. Alcohol, narcotics, amphetamines, caffeine, Reserpine, Clonodine, certain antidepressants, steroids, L-dopa, Theophylline, nicotine and others. Withdrawal from benzodiazapines, barbituates and alcohol can also be factors.
Other sleep disorders. Sleep apnea, nocturnal myoclonus, periodic leg movements in sleep, phase advance sleep disorder, phase delay sleep disorder, sleep state misperception and nightmares.
Poor sleep habits. Extended time in bed, napping or an irregular sleep schedule.
Situational factors. Stress, bereavement, unfamiliar sleep environment, jet lag, shift work, bed partner or a poor sleeping environment (noise, temperature, light or a poor sleeping surface).