You will never guess what the fifth and sixth best-selling prescription drugs are in the United States, so I’ll just tell you: Abilify and Seroquel, two powerful antipsychotics. In 2011 alone, they and other antipsychotic drugs were prescribed to 3.1 million Americans at a cost of $18.2 billion, a 13 percent increase over the previous year, according to the market research firm IMS Health. Those drugs are used to treat such serious psychiatric disorders as schizophrenia, bipolar disorder and severe major depression. But the rates of these disorders have been stable in the adult population for years. So how did...