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Two Causes of Depression

My overly oversimplification: Depression is a syndrome with at least two underlying causes. Here are two independent axes of depression. One axis is based on dopamine, which controls goal seeking drive. The other axis is based on serotonin, which controls anxiety.

Too much dopamine and you are manic. Too little and you are letharigic.

Serotonin: too much and nothing phases you - think sociopath. Too little serotonin leads to depression, sleeplessness and anxiety.
HM van Praag, Serotonin-related, anxiety/aggression-driven, stressor-precipitated depression. A psycho-biological hypothesis European Psychiatry, Volume 11, Issue 2, Pages 57-67

This has lots of detail WikiPedia: Biology of Depression, but it still treats depression as a single disease, rather than a syndrome with multiple underlying causes.

Below are totally random notes, which I hope to organize...

Mood

Definition: Particular state of mind or emotion
vs. Emotion: a mental state that arises spontaneously.

POMS, which proposed 8 basic moods, termed tension/anxiety, depression/dejection, fatigue, hostility, confusion, friendliness, elation and vigor. Note, there are only 6 moods in the WikiPedia article: Profile of Mood States

The two big factors Watson and Tellegen demonstrated were termed Positive and Negative Affect. Positive Affect represented the varieties of enjoyable engagement, Negative Affect represented the varieties of unpleasant engagement. WikiPedia: Dispositional Affect.

Gray's biopsychological theory of personality

Behavioral Activating System (BAS). It regulates such behaviors as exploration and pursuit.

Behavioral Inhibition System (BIS). It inhibits the very behaviors the BAS activates. Anthropomorphically, this is the agency that tells the animal what it mustn't do, and it keeps the animal from doing it.

The more clearly understood and widely agreed upon of these is the dopamine mediated BAS.

Less agreement exists about the correct understanding of the activity of the BIS. What is agreed is that increased activity in this system inhibits behavior.

lots more...

Stimulated by a private communication from J. Alexander Bodkin, M.D., entitled SPECULATIVE PSYCHOPHARMACOLGY: A MODEL OF THE NEUROBIOLOGY OF MOOD TO GUIDE CLINICAL PRACTICE, 1993

http://www.jch.com/jch/notes/DualAxisDerpression.html 2012.03.31 jch