1.   National Institutes of Health studies have linked low levels of a brain chemical called serotonin to abnormally aggressive or violent behavior.

2.   Specifically, dexfenfluramine boosts the activity of a brain chemical called serotonin, she notes, adding that a serotonin deficiency underlies both carbohydrate craving and depression.

3.   The experts explain that a brain chemical called serotonin can affect mood and appetite.

4.   Underlying these emotional issues, doctors say, may be an imbalance of a brain chemical called serotonin, known to be linked to depression.