One or more pain symptoms are present in 65% of people who have depression, and anywhere from 5 to 85% of people who are experiencing pain will also have depression, depending on the setting—a lower prevalence in general practice, and higher in specialty clinics. Depression is often underrecognized, and therefore undertreated, in patients presenting with pain. Depression often coexists with physical disorders common among the elderly, such as stroke, other cardiovascular diseases, Parkinsons disease, and chronic obstructive pulmonary disease. History
The Ancient Greek physician Hippocrates described a syndrome of melancholia (μελαγχολία, melankholía) as a distinct disease with particular mental and physical symptoms; he characterized all "fears and despondencies, if they last a long time" as being symptomatic of the ailment. It was a similar but far broader concept than todays depression; prominence was given to a clustering of the symptoms of sadness, dejection, and despondency, and often fear, anger, delusions and obsessions were included. The term depression itself was derived from the Latin verb deprimere, meaning "to press down". From the 14th century, "to depress" meant to subjugate or to bring down in spirits. It was used in 1665 in English author Richard Bakers Chronicle to refer to someone having "a great depression of spirit", and by English author Samuel Johnson in a similar sense in 1753. The term also came into use in physiology and economics.
Insomnia is common; in the typical pattern, a person wakes very early and cannot get back to sleep. Hypersomnia, or oversleeping, can also happen. Some antidepressants may also cause insomnia due to their stimulating effect. In severe cases, depressed people may have psychotic symptoms. These symptoms include delusions or, less commonly, hallucinations, usually unpleasant. People who have had previous episodes with psychotic symptoms are more likely to have them with future episodes.A depressed person may report multiple physical symptoms such as fatigue, headaches, or digestive problems; physical complaints are the most common presenting problem in developing countries, according to the World Health Organizations criteria for depression. Appetite often decreases, resulting in weight loss, although increased appetite and weight gain occasionally occur. Family and friends may notice agitation or lethargy. Older depressed people may have cognitive symptoms of recent onset, such as forgetfulness, and a more noticeable slowing of movements.Depressed children may often display an irritable rather than a depressed mood; most lose interest in school and show a steep decline in academic performance. Diagnosis may be delayed or missed when symptoms are interpreted as "normal moodiness." Elderly people may not present with classical depressive symptoms. Diagnosis and treatment is further complicated in that the elderly are often simultaneously treated with a number of other drugs, and often have other concurrent diseases. Cause
The biopsychosocial model proposes that biological, psychological, and social factors all play a role in causing depression.