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Cannabis and Mental Health

Cannabis and Mental Health. Sir Robin M Murray, FRS Institute of Psychiatry, London UK robin.murray@kcl.ac.uk. Most people who use cannabis don’t develop problems. Psychosis. 30. Cannabis Use. No of times cannabis taken. 0. 1. 10. >50. 2. <50. 0. 10. 20.

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Cannabis and Mental Health

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  1. Cannabis and Mental Health Sir Robin M Murray, FRS Institute of Psychiatry, London UK robin.murray@kcl.ac.uk

  2. Most people who use cannabis don’t develop problems

  3. Psychosis 30 Cannabis Use No of times cannabis taken 0 1 10 >50 2 <50 0 10 20 Swedish Army Study of Andréasson et al 1987 Cases of Sz per 1,000 Longitudinal Studies Risk of schizophrenia-likepsychosis at age 26 years FU 25 yrs 3 yrs 3 yrs Retro 3 yrs 15 yrs 4 yrs 18 mths 14 yrs OR 3.1 2.8 12.0 3.2 1.8 3.1 1.7 1.5 2.2 Country Sweden NL NL NL NZ (Chr) NZ (Dun) Germany UK Australia n 50,053 4,045 4,045 18,000 1,265 1,253 2,436 8,500 3,800 Arseneault et al 2002 Oddsratio

  4. Tetrahydrocannabinol (THC) – partial agonist at CB1 High doses cause impairment of attention, memory and learning, hallucinations and paranoid ideas Cannabidiol (CBD) – inverse agonist at CB1 Is not hallucinogenic Has anxiety relieving properties Antagonises effects of THC The ingredients of cannabis CBD THC

  5. THC causes Impairment of attention,memory and learning Hallucinations and paranoid ideas Cannabidiol (CBD) Is not hallucinogenic Has anxiety relieving properties Antagonises effects of THC The ingredients of cannabis THC CBD

  6. THCcontent(%) 14 12 10 8 6 4 2 0 1995 1996 1997 1998 1999 2000 2001 2002 2004 Cannabis potency in England Skunk Imported Herbal Resin 2008 Potter et al 2008, DoH, 2008

  7. Risk of being a Psychotic Case (OR adjusted for gender, age, ethnicity, Stimulants, level of Ed) OR

  8. Why do only some cannabis users go psychotic? Cannabis Use Psychosis Vulnerability

  9. The major unresolved issue concerns cognition • Lots of studies show that heavy cannabis users have impaired cognition • Some studies show that prolonged abstinence improves most of what has been lost • Last year follow-up of the Dunedin cohort reported that those who had started using cannabis as adolescent had lost 8 points of IQ by 38 years

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