Kleptomania is an impulse control disorder often related to other mood disorders, such as depression, substance abuse, or eating disorders. But not everyone who shoplifts is a kleptomaniac.
Kleptomaniacs do not steal because they want a particular item and can't afford it. In fact, they often discard stolen items, or secretly return them to the store from which they were taken. Instead, kleptomaniacs are driven by an uncontrollable urge to steal things. They often feel increased anxiety when the craving hits, and this can only be relieved by taking the desired item. Often they are not even fully aware that they have stolen the item.

True kleptomania is quite rare, and symptoms may appear as early as age five. About 1 percent of people who shoplift are diagnosed with kleptomania; roughly 5 percent exhibit symptoms of the disorder. The behavior is often triggered by major stressful events, although scientists aren't sure what causes it. They suspect it may be due to a chemical imbalance, particularly the brain chemical serotonin. That's because people who suffer from kleptomania are sometimes successfully treated with Prozac and other antidepressants. However, this may be because the drugs treat the other mood disorders that often accompany kleptomania, not kleptomania itself.
