Results of a new study may explain why some people who take the anti-cholesterol drugs known as statins report feelings of anxiety and depression.

Researchers studied the effects of the statin drug mevastatin in animal models.

In lab tests using human serotonin receptors expressed in animal cells, they showed that long-term use of the drug caused significant changes in the structure and function of serotonin cell receptors, which are known to influence mood and behavior. Adding cholesterol to cells treated with mevastatin restored them to normal.

The scientists say the results represent the effect of long-term cholesterol depletion on this type of cell receptor and suggest that chronic, low cholesterol levels in the brain might trigger anxiety and depression.

Statins are routinely prescribed to treat high cholesterol and have been credited with helping millions to avoid heart attacks and strokes. In addition, healthcare experts say these medications generally have few negative side effects.

Eating a healthy diet and getting regular exercise are often considered key to keeping cholesterol in check. Among the herbs and nutritional supplements believed to help lower cholesterol are fish oil, flaxseed, garlic, blond psyllium, guggulipid extract, green tea extract and beta sitosterol.