Tell Me More About Depression.
4. Everyone gets depressed. How is a major depressive episode different?
The diagnosis of a major depressive episode is based on experiencing a number of symptoms, more or less constantly for at least two weeks, although often months or years pass before people seek treatment. It is not the same as being unhappy, "down" or stressed out. It is an illness, not a temporary state of mind.
Is there a test for depression?
Although some blood tests may be abnormal in depressive disorders (eg. challenges to the cortisol system), these tests are not specific or reliable enough for diagnostic purposes. There are some promising research techniques to examine brain structure (MRI) and brain function (PET, fMRI). One part of the brain that is involved in memory function (the hippocampus) appears to be reduced in volume in patients with chronic depression. However, none of these techniques can be used routinely to make a reliable diagnosis. The diagnosis is made by a physician actively listening to the history of your problems.
References:
Mayberg HS. Modulating dysfunctional limbic-cortical circuits in depression: towards development of brain-based algorithms for diagnosis and optimised treatment. Br Med Bull 2003;65:193-207.
Drevets WC. Neuroimaging studies of mood disorders. Biol Psychiatry 2000;48:813-829.
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