Doctors have a lot of standard medications they use to treat many common physical disorders. For example, when I hit the diabetes border, my doctor prescribed metformin, a reliable (and inexpensive) drug to help control my blood sugar. It has worked admirably and the only side effect disappeared after a few weeks.

It's different with mental illnesses. While there are basically four types of drugs that are used in treating bipolar disorder, within each of those types is a bewildering array of...