With 40 percent of all heart attacks and related cardiovascular problems occurring in people who have low levels of so-called “good” cholesterol, researchers have long sought medications to increase the amount of this type of cholesterol in the body’s circulation.But a new review of 31 randomized controlled trials published in the Journal of the American Medical Association suggests that so far, only modest evidence supports the use of most medications to raise levels of high-density lipoprotein (HDL) — good cholesterol. Some are even harmful.