Atypical Depression (AD) is a subtype of Major Depression characterized by mood reactivity — being able to experience improved mood in response to positive events. In contrast, sufferers of "melancholic" depression generally cannot experience positive moods, even when good things happen. Additionally, atypical depression is characterized by reversed vegetative symptoms, namely over-eating and over-sleeping.

Despite its name, "atypical" depression is actually the most common subtype of depression — up to 40% of the depressed population may be classified as having atypical depression.

Diagnostic criteria (DSM-IV-TR)

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The DSM-IV-TR, a widely used manual for diagnosing mental disorders, defines Major Depressive Disorder with Atypical Features as a subtype of depression characterized by:

A. Mood reactivity (i.e., mood brightens in response to actual or potential positive events)

B. At least two of the following:

1. Significant weight gain or increase in appetite
2. Hypersomnia (sleeping too much, as opposed to the insomnia present in melancholic depression)
3. Leaden paralysis (i.e., heavy, leaden feelings in arms or legs)
4. long-standing pattern of interpersonal rejection sensitivity (not limited to episodes of mood disturbance) that results in significant social or occupational impairment

C. Criteria are not met for Melancholic Depression or Catatonic Depression during the same episode.

By the ICD-10 classification, it will fall in the category of F32 or F39.

Research

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In general, atypical depression tends to cause greater functional impairment than other forms of depression. Atypical depression tends to occur earlier in life than other forms of depression — usually beginning in teenage years. Similarly, patients with atypical depression are more likely to suffer from other mental illnesses such as social phobia, avoidant personality disorder, or body dysmorphic disorder. Atypical depression is more common in females — nearly 70% of the atypical population are women.

It is not yet entirely clear how atypical depression responds to treatment as compared with melacholic depression. Some studies suggest that an older class of drugs, MAOIs, may be more effective at treating atypical depression than the more modern tricyclic antidepressant and SSRIs.

It has been noted that patients with atypical depression often suffer from intense cravings for carbohydrates. A mineral supplement, chromium picolinate, was found to assuage these cravings in at least one study.

It has been hypothesized that atypical depression may be related to thyroid dysregulation. Some studies have found subtle thyroid abnormalities in people with atypical depression. Another study suggests that patients may benefit from triiodothyronine, a medication used to treat hypothyroidism.

References

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1. Atypical Depression Actually Very Typical
2. Atypical Depression
3. Atypical Depression and Triiodothyronine
4. Atypical Depression and Hypothalamic-Pituitary-Adrenal function
5. Chromium treatment for cravings in atypical depression

Also see Clinical depression.

Psychiatry | Mood disorders