Insomnia is a symptom, not a disease. Insomnia can have many causes, but the biggest cause is due to stress. Stress related to work, school, health or family concerns. Depression is the second biggest cause. The use of stimulants, including caffeine, alcohol, nicotine or other over-the-counter or prescription medications will also cause insomnia. Prescription drugs, including some antidepressant, high blood pressure and steroid medications, can interfere with sleep. Many over-the-counter medications, including some brands of aspirin, decongestants and weight loss products, contain caffeine and other stimulants. Change in your environment or work schedule and even long-term use of sleep medications will actually interrupt your sleep cycle. Medical problems, including fibromyalgia or complex diseases of the nerves and muscles can make it very difficult to fall asleep and stay asleep.