What is depression
Depression is a mental health disorder that can affect the way you eat and sleep, the way you feel about yourself, and the way you think about things. A depressive disorder is more than a passing mood. It is not a sign of personal weakness, and it cannot be willed or wished away.
A depressive disorder involves the body, mood, and thoughts. People who are depressed cannot “snap out of it” and get better. Without treatment, symptoms can last for months or years. Treatments such as antidepressant medications and psychotherapy can reduce and sometimes eliminate the
What causes depression?

The exact cause is not known. Anyone can become depressed. Some people are more prone to it, and it can develop for no apparent reason. You may have no particular problem or worry, but symptoms can develop quite suddenly. An episode of depression may also be triggered by a life event such as relationship problem, bereavement, redundancy, illness, etc. In many people it is a mixture of the two.
Heredity: Certain types of depression seem to run in certain families. Research is ongoing as to exactly which genes are involved in depression. Just because someone is your family has depression, however, doesn’t mean you will.

The causes of clinical depression are likely to be different for different people. Sometimes a depressive episode can appear to come out of nowhere at a time when everything seems to be going fine.

Symptoms of depression.
Low Mood – when you feel low, sad, empty, are easily brought to tears and experience frequent periods of irritability
Decrease in Pleasure (Anhedonia) – when you have lost most or all interest in activities you enjoy, even routine activities .

Motor Problems – you may feel physically agitated and restless or slowed down in motion
Foggy Headed – your ability to think seems decreased or your thinking seems clouded and you are unable to make any decisions

Lifestyle factors- Many of the unhealthy lifestyle habits that contribute to illnesses such as heart disease can also trigger anxiety & depression. High levels of stress or anxiety combined with poor eating and sleeping habits, and no exercise for prolonged periods may be a significant factor in some people’s experience of depression. Genetic

Prevention
Healthy lifestyle habits can help prevent depression, or lessen the chances of it happening again. These habits include eating properly, sleeping adequately, exercising regularly, learning to relax, and not drinking alcohol or using drugs.
Counseling may help you through times of grief, stress, or low mood. Family therapy may be particularly important for teens who feel blue.

Treatment
The first step in the treatment of depression is a physical examination. This is done to rule out disorders like thyroid disease, anemia or a recent viral infection, which can produce symptoms similar to those found in a depressive illness. In an estimated 20 to 25 % of major depressive episodes, the cause is an underlying factor such as a particular medication or a medical condition.
Medications
Dozens of medications are available to treat depression. Most people find the best relief of depression symptoms by combining medications and psychotherapy. Some medications for depression are antidepressants that have been specifically approved by the Food and Drug Administration (FDA) to treat depression.