Study: Alcohol 'most harmful drug,' followed by crack and heroin

London, England (CNN) -- Alcohol ranks "most harmful" among a list of 20 drugs -- beating out crack and heroin -- according to study results released by a British medical journal.

A panel of experts weighed the physical, psychological and social problems caused by the drugs and determined that alcohol was the most harmful overall, according to an article on the study released by The Lancet Sunday.