Prozac is the most commonly prescribed antidepressant in the United States. In 1999, 135 million prescriptions were written for antidepressants, with Prozac (fluoxetine) the most commonly used.

Among the newer drugs, Prozac and other serotonin reuptake inhibitors (SSRIs) are as effective as the drugs formerly used for depression, but have fewer serious side effects. Another advantage is their effectiveness with other psychiatric conditions, such as post-traumatic stress disorder, anxiety, panic disorder, and eating disorders. In 2002, the U.S. Food and Drug Administration approve Prozac for bulimia nervosa, a disorder characterized by binge eating followed by purging or other efforts to lose weight.

Prozac blocks the reuptake of the chemical serotonin, which is believed to be plentiful in the areas of the brain controlling emotion. However, the brain's biochemical pathways, and serotonin's effect on emotion and mood, are not quite so simply understood. Scientists do not exactly...