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Bipolar Disorder versus Major Depressive Disorder

The Depressive Episodes that occur in Major Depressive Disorder are identical to the ones that occur in Bipolar I Disorder or Bipolar II Disorder. Therefore, when a person experiences a Major Depressive Episode, one of the main questions that the clinician must determine is whether the person's underlying condition is Major Depressive Disorder or Bipolar Disorder.

The only difference between Major Depressive Disorder and Bipolar Disorder is that in Bipolar Disorder a person has experienced at least one Hypomanic or Manic Episode in their lifetime. Finding this out is not always an easy task, especially if the person has difficulty remembering details from their past that might help the clinician decide whether the person has ever once experienced a Hypomanic or Manic Episode.

However, this remains a very important clinical question. The treatments for Bipolar Disorder are very different from those used for Major Depressive Disorder. If a person with Bipolar Disorder is given medications for Major Depression, their condition can get seriously worse. Also, there is evidence that a large percentage of depressed patients who attempt suicide actually have unrecognized symptoms of Bipolar Disorder [ref].

Some studies have found that among young people initially diagnosed with Major Depressive Disorder, over a third of them will eventually show signs of having Bipolar Disorder [ref]. Unfortunately, in many cases this will not be recognized by the treating physician, and as many as 45% of individuals with Bipolar Disorder are misdiagnosed with Major Depressive Disorder [ref].

The best way to avoid this situation is for the clinician to take a very thorough and complete history from the patient. Questionnaires like the Mood Disorders Questionnaire can also help, where endorsement of two or more manic symtpoms should alert the physician to explore potential past Manic or Hypomanic Episodes in greater depth.

In addition, there are several clinical clues that ought to raise one's suspicion that a person with Depression may in fact have an underlying Bipolar Disorder:

Antidepressants cause the person to experience certain Manic symptoms. This can include the classic Manic symptoms like racing thoughts, irritability and a decreased need for sleep, but the person may also report feeling more anxious, agitated, "hyper" or restless.  When an antidepressant causes a full-fledged switch to Hypomania or Mania this is easier to pick-up, and in these cases a diagnosis of Bipolar Disorder ought to be very strongly considered. But in many cases individuals taking antidepressants will develop just a few Manic symptoms, and their main complaint may simply be that the antidepressants make them feel generally worse.  These reactions usually happen very quickly once the antidepressant is started, but not always. They can also occur in a particular individual with some antidepressants and not others. Any of these occurrences should alert one to the possibility that the person may have an underlying Bipolar Disorder.

The person does not respond well to antidepressants for treatment of their Depressive Episode. In these cases, the person may have an underlying Bipolar Disorder [ref].

Rapid onset of the Depressive Episode (less than one week from first symptoms to full syndrome) is more common in Bipolar Disorder [ref].

Marked irritability, agitation, labile moods or very intense anxiety are prominent features of the patient’s Depressive Episode.  These symptoms can also occur in Major Depressive Disorder, but they should increase one’s suspicion of Bipolar Disorder [ref]

The person has Depressive Episodes with Atypical Features. This increases the chances that the person may have Bipolar Disorder [ref].

There is a seasonal pattern to the person's Depressions (Seasonal Affective Disorder) [ref], and in the summer they tend to feel “very good” with lots of energy and enthusiasm. This increases the chances that the person may have Bipolar Disorder.

One's first Depressive Episode occured in one's youth (before age 25 as a rough cut-off) [ref]. The earlier the onset of the Depressions - meaning into adolescence and even childhood - the greater the chances that the true diagnosis is Bipolar Disorder.

Having a Depressive Episode with Psychotic Features increases one's chances of eventually being diagnosed with Bipolar Disorder [ref].

A family history of Bipolar Disorder increases one's chances of having this condition.

A woman who experiences a Postpartum Psychosis should be considered as having Bipolar Disorder until proven otherwise.

Postpartum Depression will turn out to be part of an underlying Bipolar Disorder in about half of all cases [ref].


Diagnosing Depression

Causes of Depression