A large study that reviewed 23 randomized clinical trials found that statins do not cause most of the side effects listed on their labels. Memory problems, depression, sleep disturbances, weight gain, and many other symptoms occurred as often in patients taking statins as in those receiving a placebo. Only a few side effects have shown an association with statins. These associated effects were even rare. The study thus confirmed that the vast majority of reported side effects are not caused by the drugs themselves.