First Sentence

"Depression is a common disorder that involves depressed mood and/or near-complete loss of interest or pleasure in activities that were previously enjoyed;somatic (eg,weight change,sleep disturbance) & cognitive manifestations (eg, difficulty concentrating) are common.Depression may markedly impair the ability to function at work & to interact socially;risk of suicide is significant.Depressive disorders occur at any age but typically develop during the mid-teens, 20s, or 30s.Exact cause of depressive disorders is unknown, but genetic & environmental factors contribute.Sometimes depressive symptoms are caused by physical disorders (eg, thyroid or adrenal gland disorders, benign or malignant brain tumors, stroke, AIDS, Parkinson disease,multiple sclerosis) or use of certain drugs(eg, corticosteroids, some beta-blockers, interferon, reserpine, ...). Diagnosis is based on clinical criteria; physical disorders must be ruled out by clinical evaluation & selected testing (CBC; electrolyte, TSH, B12 & folate levels). Treatment involves psychotherapy & usually drugs; SSRIs are usually tried first, & if they are ineffective,other drugs that affect serotonin and/or norepinephrine may be tried."