Unlike the U.S., the British government maintains an independent group of scientific experts to advise it on drug policy, called the Advisory Council on the Misuse of Drugs. In 2005, concerned about reports linking marijuana use to mental illness, the government asked the Council to take another look at the 2004 “downgrading” of marijuana, which had placed it in the least harmful category of illicit drugs and eliminated most marijuana possession arrests. The Council recommended continuing the reduced penalties, noting that teen marijuana use in Britain was declining before reclassification and has continued declining since reclassification. As for mental illness fears, “the current evidence suggests, at worst, that using cannabis increases the lifetime risk of developing schizophrenia by 1%,” and scant evidence of a causal association between cannabis use and development of depression, bipolar disorder or anxiety. (see also, “The Classification of Cannabis under the Misuse of Drugs Act 1971,” and “Cannabis Classification and Public Health (2008)”)
Advisory Council on the Misuse of Drugs, “Further Consideration of the Classification of Cannabis under the Misuse of Drugs Act 1971,” (London: Home Office, January, 2006), 36.
Full text report available online at: http://drugs.homeoffice.gov.uk/publication-search/acmd/cannabis-reclass-2005