Many drugs that treat bodily ills can alter mood, memory and other mental functions. Often the trials required to approve new drugs miss these uncommon side effects, but when the medications go on the market and are doled out to millions, thousands of people can be at risk. The drugs listed below are some of the most commonly prescribed in America; each one (including its generic versions) likely causes at least 10,000 patients—some, more than 100,000—to experience mental side effects every year.