Discontent with the quantity or pattern of sleep, even though there is opportunity to sleep. It is very rare not to be able to sleep at all; even those who maintain that they ‘haven’t slept a wink’ in fact sleep perfectly well from time to time. It is quite normal to sleep less with age. The term insomnia is usually reserved for patients who cannot function properly during the day. Problems can occur in getting to sleep, or because the patient wakes during the night, or too early, and cannot get back to sleep. Waking too early in the morning can be a symptom of endogenous depression. Difficulties in getting to sleep are common if the patient has been particularly active in the course of the evening, and cannot relax enough to sleep. Some people sleep badly after taking coffee, tea or chocolate, or if they have smoked heavily or eaten a big meal shortly before going to bed. Pain or cold also prevent sleep, because muscles cannot relax sufficiently. Interrupted sleep can be caused by the consumption of quantities of alcohol; it is easy enough to get to sleep, but after a few hours the kidneys begin to produce more urine and the patient has to get up, and then often cannot get back to sleep again. Other causes of sleep disorders are anxiety, tension or psychosocial problems.