Wikipedia defines depression as a state of low mood and aversion to activity. This can be caused by life events, and perhaps even triggered by a medical problem or medical treatments. The National Institute of Mental Health defines the following types of depression:
- Major depression - combination of symptoms that interfere with a person's life. Most need treatment to get better.
- Dysthymia - Long term, greater than 2 years of symptoms that are not disabling, but degrade quality of life. Usually victims endure one or more major depression episodes in their life.
- Minor depression - symptoms for two weeks, but not of the severity of major depression. Without treatment, it can result in major depression.
- Bipolar disorder - cycling mood change from extreme highs to extreme lows.
Genetic Switch Involved in Depression tells that the activity of a single gene can result in physical brain changes associated with depression. Ronald Duman's group of Yale University researchers used DNA microarray chips to analyze the activity of 20,000 genes in patients with depression.
About 30 percent of the lower gene activity in the patients was related to some aspect of synapse function. More focused investigation identified 5 particular genes in the prefrontal cortex of depressed people. The researchers searched for proteins that could turn these genes on or off. GATA1 is such a protein and is found in the brains of patients with major depressive disorder. It can also result in a higher rat model of depression.
Laboratory cultures of GATA1 shows it decreases the expression of synapse-related neurons.
The next step in the research is to find a way to increase the expression of synapse connections, perhaps leading to more effective antidepressant therapies.