What Is Depression?

Depression is a mental illness marked by feelings of profound sadness and lack of interest in activities. Depression is not the same as “the blues,” which anyone can feel from time to time. It is a persistent, depressed mood that interferes with the ability to function and enjoy usual interests. It may cause a wide range of symptoms, both physical and emotional, and can last for weeks, months, or years. People with depression rarely recover without treatment. There are many types of depression, including the following.

  • Major Depression, also called unipolar depression, is a serious episode of depressive symptoms that are severe enough to interfere with a person’s ability to function.
  • Bipolar Depression refers to the depressive symptoms experienced by people with bipolar disorder, which is a mood disorder that cycles between periods of mania and depression.
  • Dysthymia is a mild to moderate form of chronic depression (lasting at least two years).
  • Postpartum Depression occurs in some women after childbirth, and could be caused by hormonal changes.
  • Seasonal Affective Disorder (SAD) is a worsening of depression symptoms during the winter months, thought to be caused by decreased exposure to sunlight.

Symptoms of Depression

Depression symptoms can differ from person to person. Some people have only a few symptoms, while others have many. Symptoms can change over time and may include:

  • Persistent feelings of sadness, anxiety, or emptiness
  • Hopelessness
  • Feelings of guilt, worthlessness, or helplessness
  • Loss of interest in hobbies and activities
  • Loss of interest in sex
  • Feeling tired
  • Difficulty concentrating, remembering, or making decisions
  • Difficulty with sleep (waking up too early or oversleeping)
  • Eating more or less than usual
  • Weight gain or weight loss
  • Thoughts of death or suicide, with or without suicide attempts
  • Restlessness or irritability
  • Physical symptoms that defy standard diagnosis and do not respond well to medical treatments

Causes of Depression

There is no known single cause for depression. Most research studies suggest depression stems from a combination of psychological, physical, and environmental factors, including:

  • Stressful life events (usually in combination with one or more of the following causes)
  • Chronic stress
  • Low self-esteem
  • Imbalances in brain chemicals and hormones
  • Lack of control over circumstances (helplessness and hopelessness)
  • Negative thought patterns and beliefs
  • Chronic medical illnesses and/or chronic pain
  • Genetic predisposition
  • Altered brain structure and function, resulting from causes such as stroke
  • Diseases such as Parkinson’s, cancer, hypothyroidism, anemia, and heart disease (and heart surgery)
  • Substance abuse

Risk Factors for Depression

Factors that increase the risk of developing depression include:

  • Female gender
  • Certain chronic medical diseases such as hypothyroidism, cardiovascular illness, diabetes, arthritis, gastrointestinal disorders (Crohn’s), many forms of cancer, and neurological disorders such as stroke or Parkinson’s disease.
  • Previous episodes of depression
  • Major life changes or stressful life events (e.g., bereavement, trauma)
  • Winter season for SAD
  • Little or no social support
  • Low self-esteem or perceived lack of personal control over circumstances
  • Family history of depression (parent or sibling)
  • Certain medications used to treat medical conditions (such as steroids) can be associated with depression
  • Substance abuse
  • Smoking
  • Poor sleep habits

Diagnosis for Depression

There is no single diagnostic test for depression. The doctor will ask about a patient’s symptoms and medical history, giving special attention to factors such as alcohol and drug use, thoughts of death or suicide, family members who have had depression, sleep patterns, and previous episodes of depression.

The doctor may also perform specific mental health exams to gather detailed information about a patient’s speech, thoughts, memory, and mood. A physical exam and other laboratory tests can help rule out other causes of depressive symptoms.