What Is Major Depressive Disorder?

According to the National Institute of Mental Health, major depressive disorder is characterized by a combination of symptoms that interfere with a person’s ability to work, sleep, study, eat, and enjoy once-pleasurable activities.

There are times you may feel sad, lonely, or hopeless for a few days. But major depression — clinical depression — is disabling. It can prevent you from functioning normally. An episode of clinical depression may occur only once in a person’s lifetime. More often, though, it recurs throughout a person’s life.

In addition, with major depression, one of the symptoms must be either depressed mood or loss of interest. The symptoms should be present daily or for most of the day or nearly daily for at least two weeks. Also, the depressive symptoms must cause clinically significant distress or impairment in functioning. The symptoms cannot be due to the direct effects of a substance — drug abuse, medications — or a medical condition, such as hypothyroidism, nor occur within two months of the loss of a loved one.

What Is Chronic Depression or Dysthymia?

Chronic depression, or dysthymia, is characterized by a long-term (two years or more) depressed mood. Chronic depression is less severe than major depression and typically does not disable the person. If you have dysthymia or chronic depression, you may also experience one or more episodes of major depression during your lifetime.

What Is Atypical Depression?

The key symptoms of atypical depression include:

• Overeating
• Oversleeping
• Fatigue
• Extreme sensitivity to rejection
• Moods that worsen or improve in direct response to events

Regular depression, on the other hand, tends to be marked by pervasive sadness.

What Is Bipolar Depression or Manic Depression?

Bipolar disorder — sometimes referred to as manic depression — is a complex mood disorder that alternates between periods of clinical depression and times of extreme elation or mania. There are two subtypes of bipolar disorder: bipolar I and bipolar II.

With bipolar I disorder, patients have a history of at least one manic episode with or without major depressive episodes.

With bipolar II disorder, patients have a history of at least one episode of major depression and at least one hypomanic (mildly elated) episode.

How Is Seasonal Depression (SAD) Different From Other Types of Depression?

Seasonal depression, often called seasonal affective disorder or SAD, is a depression that occurs each year at the same time. It usually starts in the fall or winter and ends in spring or early summer. It is more than just “the winter blues” or “cabin fever.” A rare form of SAD, known as “summer depression,” begins in late spring or early summer and ends in fall.