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 at 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, handwringing) 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 tumor 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.
Depression is among the most treatable of mental disorders. Between 80% and 90% percent 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 with the goal of arriving at a diagnosis and planning a course of action.