This is one of the syndromes that can make your life worthless. Run from it. But before then, read this to get clarifications

Depression (major depressive disorder) is a common and serious medical illness that negatively affects how you feel, the way you think and how you act. Fortunately, it is also treatable. Depression causes feelings of sadness and/or a loss of interest in activities you once enjoyed. It can lead to a variety of emotional and physical problems and can decrease your ability to function at work and home.

Depression symptoms can vary from mild to severe and can include:

Feeling sad or having a depressed mood

Loss of interest or pleasure in activities once enjoyed

Changes in appetite — weight loss or gain unrelated to dieting

Trouble sleeping or sleeping too much

Loss of energy or increased fatigue

Increase in purposeless physical activity (e.g., inability to sit still, pacing, hand-wringing) or slowed movements or speech (these actions must be severe enough to be observable by others)

Feeling worthless or guilty

Difficulty thinking, concentrating or making decisions

Thoughts of death or suicide

Symptoms must last at least two weeks and must represent a change in your previous level of functioning for a diagnosis of depression.

Also, medical conditions (e.g., thyroid problems, a brain tumour or vitamin deficiency) can mimic symptoms of depression so it is important to rule out general medical causes.

Depression affects an estimated one in 15 adults (6.7%) in any given year. And one in six people (16.6%) will experience depression at some time in their life. Depression can occur at any time, but on average, first appears during the late teens to mid-20s. Women are more likely than men to experience depression. Some studies show that one-third of women will experience a major depressive episode in their lifetime. There is a high degree of heritability (approximately 40%) when first-degree relatives (parents/children/siblings) have depression.
How Is Depression Treated?

Depression is among the most treatable mental disorders. Between 80% and 90% per cent of people with depression eventually respond well to treatment. Almost all patients gain some relief from their symptoms.

Before a diagnosis or treatment, a health professional should conduct a thorough diagnostic evaluation, including an interview and a physical examination. In some cases, a blood test might be done to make sure the depression is not due to a medical condition like a thyroid problem or a vitamin deficiency (reversing the medical cause would alleviate the depression-like symptoms). The evaluation will identify specific symptoms and explore medical and family histories as well as cultural and environmental factors to arrive at a diagnosis and plan a course of action.