Theory and history
Note: The name "Melancholia" (derived from 'black bile', one of the imagined 'humours' of Hippocrates' four humours theory of emotion) appears to be cognate with what is now called depression. It is also the name of an engraving by Albrecht Dürer that allegorically depicts the symptoms of depression.
Psychiatrists have attempted to categorize depression in many ways, one older division was between "reactive" or "exogenous" depressions, which were thought to be depressions caused by other medical conditions or an identifiable life trauma or loss; and "endogenous" depressions in which it is difficult to find an external cause. Often depression is repressed anger (in a person who has been oppressed or controlled) or repressed fear (in a person who has been assaulted) and hence episodes of violence and/or major anxiety can alternate with episodes of major depression. Post-traumatic stress disorder, is a form of depression noticed in persons who have been raped, and/or assaulted, in prostitutes, and military personnel and others who have experienced a lot of violence.
Current psychiatric standards do not differentiate between exogenous and endogenous depressions since research appears to show that depressions with similar symptoms have a similar natural history and response to treatment regardless of trigger.
Depressions can also be categorised as being just "unipolar depression" or being a depression that is part of bipolar disorder (also known as "manic depression"), where the patient cycles between a state of depression and a state of mania. It appears to have well-documented physical correlates. Though bipolar disorder often responds well to chemical treatment, it can be harder to treat than clinical depression. This is because the medicines that will bring the bipolar disorder patient up from the deep well of depression can cause him to shift too far into the manic part of the bipolar spectrum and vice versa.
It is theorized that unipolar depression and unipolar mania are the opposite poles of a wider bipolar spectrum.
Depression can be linked to seasonal affective disorder, and a continuing mild depression is known as dysthymia.
About 10% of women develop depression after giving birth; this is known as postpartum depression.
Biology and Depression
Abnormal neurotransmitter activity is associated with depression, especially so with serotonin. It has been suggested that many depressed individuals have low levels of this neurotransmitter, although this is not necessarily the case, with some depressed individuals possessing dysfunctionally high levels. Unfortunately good scientic evidence to support these ideas is lacking. Abnormal thyroid activity and heavy metal poisoning can both cause depression.
See also: