• Basics

    Depression is an illness that can affect thoughts, mood, and physical health. It is characterized by overwhelming feelings of sadness, emptiness, and worthlessness. With depression, these feelings are severe enough that they interfere with work and relationships Table 01.

    Depression is a long-term condition involving several symptoms that can negatively affect work, relationships, and the quality of life of those that suffer from it. About 17% of the U.S. population experiences depression at some time in their lives. Depression is more common in women but can happen to anyone, regardless of race, income, or education.

    Depression is classified as a psychiatric illness. The term “psychiatric illness” is a general term that covers a wide range of disorders. In the past, ignorance and fear contributed to a social stigma regarding psychiatric illness. It is becoming more widely known that psychiatric problems such as depression are common.

    Many people misunderstand depressive disorders. Depression is not just “feeling blue.” It is not a sign of weakness or lack of character. A person cannot “just snap out of” being depressed. These misinformed attitudes can harm depressed people by causing them to avoid acknowledging their illness and seeking treatment. Without treatment, depression can last for months, or even years.

    Depression is an illness that causes more disability than diabetes, coronary artery disease, or arthritis. The World Health Organization estimates that depression will be the second-leading cause of disability by the year 2020 Table 01.

    Table 1.  The Effects of Depression in the U.S.

    How depression impacts society
    Problems with relationships (family, friends, coworkers, spouses).
    More sick days from work.
    Decreased productivity.
    Job-related injuries.
    Poorer-quality work.
    Lost jobs.
    Failure to advance in school or career.
    Health problems resulting from depression
    Suicide attempts that result in injury or disability.
    Accidents due to depression-caused difficulty in concentrating.
    Illnesses worsened or triggered by the stress of depression.
    Illnesses caused by drug or alcohol abuse.
    Deaths resulting from depression
    There are 30,000 to 35,000 suicides per year in the U.S.
    Depression can cause deaths from accidents related to impaired concentration and attention.
    Depression can contribute to other conditions that may result in death, such as alcohol abuse.
    Depression may play a part in premature death due to other causes, such as heart disease.
  • Causes

    Depression is likely caused by a combination of biological, genetic, and psychological factors.

    The cause of depression for most people is likely a combination of biological (brain chemistry), psychosocial (life stressors), and genetic (inherited) factors. Much about depression is not yet known, and researchers continue to investigate more specific causes.

    Depression runs in families.

    If you have a close relative with a history of depression, you are 1.5 to 3 times more likely to become depressed than someone with no family history of depression. This is likely due at least in part to heredity. For example, adopted children whose biological parents have a history of depression have an increased risk for depression, even if the children's adoptive family has no history of depression. However, nongenetic factors within the environment of some families may also increase the risk of depression. Learned behavior, social environment, and economic conditions may contribute to the development of depression.

    Disturbances in brain chemistry often occur with depression. The brain requires certain chemicals to function. These chemicals are called neurotransmitters. Antidepressant drugs that increase levels of certain neurotransmitters, especially serotonin and norepinephrine, are most effective in treating depression.

    Hormones can influence depression.

    Some women regularly experience depression associated with their menstrual cycle, with symptoms improving after their period begins (when estrogen levels drop). The phenomenon of sadness following birth (postpartum depression) is also well known, and seems to be at least partly hormonally triggered.

    While much more common for women, hormonally driven episodes of depression can occur in men as well. For example, teenagers (both male and female) can become moody as a result of the hormonal fluctuations of adolescence. In addition, men who take testosterone for bodybuilding can become depressed when they stop taking the hormone. Adrenal, thyroid, and growth hormone dysfunction have also been cited as causes for depression in both men and women.

    Physical damage to the brain can trigger depression.

    Injury to the brain (such as head injury or stroke) can cause changes in mood and personality, including depression. Tests such as magnetic resonance imaging (MRI), positron emission tomography (PET), and single photon emission computed tomography (SPECT) can be useful in detecting abnormalities of the brain that may cause depression.

    Psychological causes can trigger depression.

    In the past, psychiatrists theorized that depression was caused by unconscious anger toward oneself, feelings of childhood loss, or frustration about reality not measuring up to one's aspirations. Current theories state that depression results from persistent negative thoughts about oneself or from stress caused by interpersonal conflicts.

    Psychotherapy that focuses on changing persistent negative thoughts about oneself and others (cognitive-behavioral therapy), improving relationships (interpersonal therapy), and stress reduction techniques can be effective in treating mild to moderate depression. Such psychotherapy can both relieve depression and prevent it from recurring. Psychotherapy may be used alone, or with antidepressant medication.

    Life stresses may trigger episodes of depression.

    Both men and women are particularly at risk for depression after the death of a spouse. Many remain depressed for a year after their loss. Unemployment, divorce, and serious health crises can also trigger depressive episodes. Once someone has experienced an initial episode of depression, they are at higher risk of having depression again in the future.

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