* 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). Source: Perlis, M.L. & Youngstedt, S.D. "The diagnosis of primary insomnia and treatment alternatives."Comprehensive Therapy, Vol. 26, No. 4.