Depression In bed, you toss and turn, unable to get a good night's sleep. You feel anxious and worried. There's plenty to do, but the work piles up because you feel listless and tired. You don't even want to do anything fun. Friends tell you to 'pull yourself together,' but you feel helpless and hopeless. You have difficulty concentrating and making decisions. When you look in the mirror, you hate yourself. You are definitely in one of life's valleys—you are depressed. Everyone gets the blues once in a while. Emotional lows and highs are a normal part of life. The blues become depression when you feel so sleepy and listless that you can't function normally in everyday life. Types of Depression Depression can range from a mild panic to self-destructive or suicidal behavior, It's important to understand the various types of depression so that you can recognize them. Depression occurs at all ages, although major depressive episodes peak between the ages of 55 and 70 in men and 20 and 45 in women. About half of those who experience an episode of major depression will have another within two years. For some people, episodes of depression are separated by several years, while others suffer groups of episodes over a short time span. Between episodes, such individuals feel well. Major depressive disorder affects approximately 14.8 million American adults —or 6.7 percent of the U.S. population aged 18 years and older—in a given year. Major depressive disorder is more common in women than in men. Although treatment can help more than 80 percent of people with severe depression, most people with depression do not seek treatment. -- Reactive depression. This type of depression is a reaction to stressful events—divorce, death of a loved one, a chronic illness, a personal tragedy, or even social isolation, which the elderly frequently experience. The person is unable to recover normally from the feelings associated with the event. Common feelings include self-pity, pessimism, and loss of interest in life. It affects people of all ages. -- Seasonal Affective Disorder (SAD). If you live in the northern latitudes and suffer depression during the winter months, you may suffer from seasonal affective disorder caused by a lack of exposure to sunlight. Doctors aren't sure exactly what physiological mechanisms are at work in SAD, but they speculate that depressed feelings and other symptoms may be due to an increase in the release of the hormone meltonin. SAD sufferers feel lethargic and irritable. They may also suffer from chronic headaches, increased appetite, weight gain, and an increased need for sleep. For unknown reasons, SAD is truly a 'woman's depression,' in that women make up 70 percent to 80 percent of those affected. Since about half of all SAD sufferers have relatives who also suffer from SAD or other emotional problems, researchers speculate that the problem may be inherited. -- Biochemical depression. Doctors aren't sure why, but some people develop a biochemically based depression sometime during midlife. It's likely that this type of depression is caused by biochemical problems within the brain. The problem usually responds well to antidepressant medication. You may be more likely to develop this type of chemical depression if other members of your family have also suffered from this problem. -- Disease or drug-related depression. Some diseases such as AIDS, stroke, chronic pain, and hypothyroidism (甲状腺功能减退) can cause depression. In hypothyroidism, the thyroid gland (甲状腺) malfunctions, leading to too little or no thyroid hormone circulating in the bloodstream. In addition to depression, other symptoms of hypothyroidism include fatigue, weakness, weight gain, impaired memory, and shortness of breath. Fortunately, the depression and other symptoms of hypothyroidism can be effectivel