|Other names||Depression with atypical features|
|Symptoms||Low mood, mood reactivity, hyperphagia, hypersomnia, leaden paralysis, interpersonal rejection sensitivity|
|Usual onset||Typically adolescence|
|Types||Primary anxious, primarily vegetative|
|Risk factors||Bipolar disorder, anxiety disorder, female sex|
|Differential diagnosis||Melancholic depression, anxiety disorder, bipolar disorder|
|Frequency||15-29% of depressed patients|
Atypical depression as it has been known in the DSM IV, is depression that shares many of the typical symptoms of the psychiatric syndromes of major depression or dysthymia but is characterized by improved mood in response to positive events. In contrast, people with melancholic depression generally do not experience an improved mood in response to normally pleasurable events. Atypical depression also features significant weight gain or an increased appetite, hypersomnia, a heavy sensation in the limbs and interpersonal rejection sensitivity that results in significant social or occupational impairment.
Despite its name, "atypical" depression does not mean it is uncommon or unusual. The reason for its name is twofold: (1) it was identified with its "unique" symptoms subsequent to the identification of melancholic depression and (2) its responses to the two different classes of antidepressants that were available at the time were different from melancholic depression (i.e., MAOIs had clinically significant benefits for atypical depression, while tricyclics did not).
Atypical depression is two to three times more common in women than in men. Individuals with atypical features tend to report an earlier age of onset (e.g. while in high school) of their depressive episodes, which also tend to be more chronic and only have partial remission between episodes. Younger individuals may be more likely to have atypical features, whereas older individuals may more often have episodes with melancholic features. Atypical depression has high comorbidity of anxiety disorders, carries more risk of suicidal behavior, and has distinct personality psychopathology and biological traits. Atypical depression is more common in individuals with bipolar I, bipolar II, cyclothymia and seasonal affective disorder. Depressive episodes in bipolar disorder tend to have atypical features, as does depression with seasonal patterns.
Signs and symptoms
The DSM-IV-TR defines Atypical Depression as a subtype of Major Depressive Disorder with Atypical Features, characterized by:
- Mood reactivity (i.e., mood brightens in response to actual or potential positive events)
- At least two of the following:
- Significant weight gain or increase in appetite (hyperphagia);
- Hypersomnia (sleeping too much, as opposed to the insomnia present in melancholic depression);
- Leaden paralysis (i.e., heavy feeling resulting in difficulty moving the arms or legs);
- Long-standing pattern of interpersonal rejection sensitivity (not limited to episodes of mood disturbance) that results in significant social or occupational impairment.
- Criteria are not met for With Melancholic Features or With Catatonic Features during the same episode.
While the true prevalence of atypical depression is difficult to know, several studies conducted in patients diagnosed with a depressive disorder met atypical criteria between 15% to 40%. Overall, rejection sensitivity is the most common symptom, and due to some studies forgoing this criterion, there is concern for underestimation of prevalence.
Significant overlap between atypical and other forms of depression have been observed, though studies suggest there are differentiating factors within the various pathophysiologic models of depression. In the endocrine model, evidence suggests the HPA axis is hyperactive in melancholic depression, and hypoactive in atypical depression. Furthermore, regarding the inflammatory theory of depression, inflammatory blood markers (cytokines) appear to be more elevated in atypical depression when compared to non-atypical depression.
Until the 2000s Monoamine oxidase inhibitors (MAOI) such as the original iproniazid were thought to be of superior efficacy compared to other antidepressants for the treatment of atypical depression. Since then numerous studies and meta analyses have provided mixed results, throwing doubt on the idea of select agent superiority for the treatment of atypical depression. Due to their toxicity (including hypertensive crises), MAOI are less often used by psychiatrists, even in the setting of atypical depression. There currently do not exist robust guidelines for the treatment of atypical depression.
In general, atypical depression tends to cause greater functional impairment than other forms of depression. Atypical depression is a chronic syndrome that tends to begin earlier in life than other forms of depression—usually beginning in the teenage years. Similarly, patients with atypical depression are more likely to suffer from personality disorders and anxiety disorders such as borderline personality disorder, avoidant personality disorder, generalized anxiety disorder, obsessive-compulsive disorder, and bipolar disorder.
Medication response differs between chronic atypical depression and acute melancholic depression. Some studies suggest that the older class of antidepressants, monoamine oxidase inhibitors (MAOIs), may be more effective at treating atypical depression. While the more modern SSRIs and SNRIs are usually quite effective in this illness, the tricyclic antidepressants typically are not. The wakefulness-promoting agent modafinil has shown considerable effect in combating atypical depression, maintaining this effect even after discontinuation of treatment. Antidepressant response can often be enhanced with supplemental medications, such as buspirone, bupropion, or aripiprazole. Psychotherapy, whether alone or in combination with medication, is also an effective treatment.
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