Another book that seeks to help the depressed change their brain chemistry without medication, Natural Prozac divides such people into two types. "Satiation" types seek to boost their levels of the neurotransmitter serotonin to promote relaxation, calmness, and a sense of security, and often become uncomfortable in overly arousing situations. "Arousal" types, on the other hand, eat foods and participate in activities that boost norepinephrine and dopamine, neurotransmitters related to alertness, assertiveness, and aggression; such people would rather be anxious than bored. According to Robertson, one of the ways for each of these types of people to battle depression is to act against their instincts: when satiation types raise their "excitement" chemicals and arousal types raise their "calmness" chemicals, their brains come into better balance; while this may make them anxious at first, eventually they become tolerant of the higher levels. Robertson recommends a variety of...