At the request of my right hon. Friend the Home Secretary, the Government's advisory committee on drugs, the Advisory Council on the Misuse of Drugs (ACMD), recently carried out a substantial review of the harms associated with cannabis use, including the physical and psychological effects of cannabis.
Recently, the Department commissioned a systematic review of studies in this area. The peer-reviewed results of this review were published in The Lancet in July 2007 and confirmed the increased evidence of an association, possibly causal, between prior cannabis use and later development of psychosis and schizophrenia with a 40 per cent. increase in risk reported (up to 200 per cent. increase for at-risk heavy users).
The Department has also commissioned research into the harmful components of cannabis and tobacco smoke. This work is well advanced and a publication date will be set in due course.
The Department keeps the evidence of the physical and psychological effects of cannabis under review and has commissioned the National Addiction Centre to review the evidence of harms for the Department's publication, 'Dangerousness of Drugs (2001)', copies of which have already been placed in the Library. The Department has identified funding for the review to be updated later this year.