The assessment also includes a mental state examination, which is an assessment of the person's current mood and thought content, in particular the presence of themes of hopelessness or pessimism, self-harm or suicide, and an absence of positive thoughts or plans.
The score on a rating scale alone is insufficient to diagnose depression to the satisfaction of the DSM or ICD, but it provides an indication of the severity of symptoms for a time period, so a person who scores above a given cut-off point can be more thoroughly evaluated for a depressive disorder diagnosis.
However, since the 1990s results have been inconsistent, with three recent reviews finding an effect and two finding none.
Other genes that have been linked to a Gx E interaction include CRHR1, FKBP5 and BDNF, the first two of which are related to the stress reaction of the HPA axis, and the latter of which is involved in neurogenesis.
A person having a major depressive episode usually exhibits a very low mood, which pervades all aspects of life, and an inability to experience pleasure in activities that were formerly enjoyed.
Depressed people may be preoccupied with, or ruminate over, thoughts and feelings of worthlessness, inappropriate guilt or regret, helplessness, hopelessness, and self-hatred.
Depression may also come secondary to a chronic or terminal medical conditioned such as HIV/AIDS, or asthma and may be labeled "secondary depression".
It is unknown if the underlying diseases induce depression through effect on quality of life, of through shared etiologies(such as degeneration of the basal ganglia in parkinson's disease or immune dysregulation in asthma).
HPA axis abnormalities have been suggested in depression given the association with CRHR1 with depression and the increased frequency of dexamethasone test non-suppression in depressed patients.
However this abnormality in not sensitive enough to be used as a diagnosis tool(only 44%).
Theories unifying neuroimaging findings have been proposed.
The first model proposed is the "Limbic Cortical Model", which involves hyperactivity of the ventral paralimbic regions and hypoactivity of frontal regulatory regions in emotional processing.
Depression may also be iatrogenic(the result of healthcare), such as drug induced depression.