Atypical depression is known as a form of depressive illness or condition where symptoms that are not usually seen in typical depression sufferers are present. This means that symptoms of atypical depression are not found in people with chronic depression. As doctors can't classify these atypical symptoms as a separate condition, they are usually included within a secondary diagnosis.
The people most likely to have the secondary diagnosis of atypical depression are those who suffer from severe, chronic depression, those with bipolar I disorder (known as the classic 'manic' disorder), or those suffering from bipolar II disorder (a seemingly 'softer' form of bipolar).
A study review in a 2006 paper in the Journal Psychiatry report first described the condition of atypical depression as a means of explaining why some people who displayed depressive symptoms responded better to anti-depressant medication than others did.
As with most mental disorders, the diagnosis of atypical depression is achieved through the conditions of a certain number of specific symptoms occurring within a set time period. The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders states that the conditions for atypical depression are that at least two of the four symptoms are present for at least two weeks.
The symptoms are excessive sleepiness, higher appetite, sense of heaviness within the limbs and a sensitivity to social rejection which is present even when the person in question experiences an otherwise normal mood. Two other conditions for diagnosis are that the mood of the affected person must improve under positive circumstances and neither melancholia or catatonia may be present.
People who suffer from symptoms of atypical depression may share certain personality traits in common with those who are diagnosed with borderline personality disorder, avoidant personality disorder and histrionic personality disorder. Sufferers may be more impulsive, have a reduced ability for clear thought, have a short fuse (be angered easily) and be frequently worried or anxious. People with atypical depression may also be more likely to give up on goals, underachieve and fixate on past mistakes that caused shame or embarrassment.
Bipolar I disorder is the condition that was commonly referred to as manic depression or manic disorder. This is because those who are affected by bipolar I disorder display symptoms of extreme agitation or energy (otherwise known as symptoms of mania) coupled with separate bouts of depressive symptoms which, on their own, would result in a diagnosis of depression. The two states commonly occur independently of each other and can last for weeks, months or even years. In bipolar I, the two states can also be experienced as a mix, with both depressive and manic symptoms occurring within the same episode.
The bipolar II disorder is similar to bipolar I, with one main difference. The depressive symptoms are usually of the same intensity as can be experienced with bipolar I disorder, but the manic episodes aren't quite as 'manic'. Known as the 'softer' bipolar disorder, sufferers of bipolar II often experience something known as hypomania rather than full-blown mania; this means that the symptoms are less overt and do not have the same intensity.
Atypical depression has a strong correlation and association with the depressive episodes of both bipolar I and bipolar II disorder. There is current evidence that those who are affected by symptoms of atypical depression may have a genetic predisposition toward bipolar disorders. There is thought to be a clear link between the development of atypical depression and the depressive episodes of bipolar II disorder, with over half of bipolar II suffers displaying probable atypical depression.
People affected by the bipolar conditions can display atypical depression symptoms earlier than people with other depressive conditions. Those with the conditions may also experience longer and possibly more frequent depressive episodes with a higher concentration of excessive sleepiness or heaviness of the limbs.
Regardless of whether atypical depression is in correlation with a bipolar disorder, the risks to those who suffer from the conditions can be debilitating, and the individual may be reluctant to seek help. Depressions can cause increased risk of suicide, social anxiety and withdrawal, a tendency to fight with loved ones, aggression and secrecy, an increased risk of substance abuse, a higher likelihood of addiction and the inability to look after oneself adequately (including severe weight loss and bad personal hygiene).