Physical illness or chronic pain can also trigger a depressive episode. Environmental factors such as poverty, abuse, and even the amount of daylight can have a profound effect on one's mood. Most people have known someone who has suffered from a major depression, or they have struggled with it themselves. Overwhelming feelings of sadness are the trademark. The symptoms experienced by my friend are characteristic of a major depression, weight loss, difficulty sleeping, and loss of interest in everyday activities.
Dysthymia is a low level depression that lasts at least two years in adults.
While the symptoms are not as severe as major depression, dysthymia can intrude on daily life, leaving the individual feeling generally low, with little enjoyment in life. Bipolar disorder is characterized by periods of depression which give way to manic episodes. During a manic episode the individual can experience highly elated and erratic feelings, taking the form of grandiose ideas, an urgent need to talk, racing thoughts, less need for regular sleep. Sometimes manic individuals will experience overwhelming urges to shop and spend money, or other pleasure-seeking urges. There may be months or years between episodes of mania or there may be more rapid cycling of moods.