Atypical depression is a subtype of major depression or dysthymic disorder that involves several specific symptoms, including increased appetite or weight gain, sleepiness or excessive sleep, marked fatigue or weakness, moods that are strongly reactive to environmental circumstances, and feeling extremely sensitive to rejection.
Atypical depression can be a "specifier" for either major depression or dysthymic disorder. People with atypical depression have often experienced depression first at an early age, during their teenage years.
A person with classic major depression has at least five of the following nine symptoms:
Sadness or depressed mood most of the day or almost every day
Loss of enjoyment in things that were once pleasurable
Major change in weight (gain or loss of more than 5% of weight within a month) or appetite
Insomnia or excessive sleep almost every day
A state of physical restlessness or being rundown that is noticeable by others
Fatigue or loss of energy almost every day
Feelings of hopelessness or worthlessness or excessive guilt almost every day
Problems with concentration or making decisions almost every day
Recurring thoughts of death or suicide, suicide plan, or suicide attempt
Dysthymic disorder is a condition involving the presence of a depressed mood more days than not for at least a two year period in adults (one year in children and adolescents) plus at least two of the above associated symptoms, but fewer than the five symptoms which define a major depressive episode.
Despite its name, atypical depression is very common. It is contrasted with "melancholic" depression, another subtype of depression, involving symptoms of insomnia (rather than oversleeping), loss of appetite (rather than increased appetite), a relative lack of mood reactiveness to environmental circumstances, and a markedly diminished ability to feel pleasure.
What are the symptoms of atypical depression?
The main characteristic of atypical depression that distinguishes it from melancholic depression is mood reactivity. In other words, the person with atypical depression will see his or her mood improve if something positive happens. In melancholic depression, positive changes will seldom bring on a change in mood. In addition, diagnostic criteria call for at least two of the following symptoms to accompany the mood reactivity:
Sleeping too much (hypersomnia)
Increased appetite or weight gain
Having a more intense reaction or increased sensitivity to rejection, resulting in problems with social and work relationships
Having a feeling of being weighed down, paralyzed, or "leaden"
A doctor will investigate physical causes for any of these symptoms. That will include a physical exam and tests to look for a problem such as hypothyroidism. With hypothyroidism, having low levels of thyroid hormone can lead to symptoms that include depression and weight gain.
What causes atypical depression?
Depression is believed to be the result of impaired functioning of brain circuits that regulate mood, and that allow one region of the brain to communicate with another. Nerve cells contained within these circuits transmit signals through brain chemicals called neurotransmitters -- such as dopamine, serotonin, and norepinephrine. Antidepressant medicines are thought to "tweak" these chemicals and thereby improve the efficiency of brain circuits related to mood.