Far more harm is caused by the criminal prohibition of marijuana than by the use of marijuana itself.

According to the U.S. Department of Health and Human Services, 35 percent of adults admit to having tried marijuana. Of these, only 5 percent have used marijuana in the past year, and only 3 percent have used marijuana in the past month.
REFERENCE: U.S. Department of Health and Human Services. 2000. National Household Survey on Drug Abuse. Table G.9. Percentages Reporting Lifetime, Past Year, and Past Month Use of Illicit Drugs Among Persons Aged 26 or Older: 1999. DHHS Printing Office: Rockville, MD.