September 10, 2014

expert reaction to cannabis, suicide and reduced educational attainment

Researchers have published in The Lancet Psychiatry reporting a link between cannabis use in adolescents and suicide, further drug use and dependence, as well as reduced educational attainment.

Dr Michael Bloomfield, Academic Clinical Fellow and Honorary Clinical Lecturer in Psychiatry at the MRC Clinical Sciences, London and University College London, said:

“There is now consistent evidence that heavy cannabis use, especially during adolescence, can increase the risk of mental health problems in later life, particularly paranoid psychosis, which is typically seen in schizophrenia. Recent research has shown that THC, one of the main active ingredients in cannabis, increases anxiety symptoms, which in turn may go on to develop into paranoia. Previous research has also shown that heavy cannabis use in adolescence may be associated with poor educational and occupational outcomes later in life.

“This new, large and well-conducted study, by a respected team of scientists in Australia and New Zealand, found relationships between how much cannabis people were smoking when they were seventeen and lower rates of school and university completion in adult life.  Interestingly, this study did find that daily cannabis use at 17 increased the risk of using other illicit drugs in later life. However, of particular concern, this study found that heavy cannabis use was also associated with a significantly increased risk of suicide attempts.  The findings of this study strongly suggest that heavy cannabis use is to blame for their findings, but further research is needed to tease out cause and effect.

“This new study ties in well with previous research into the mental health effects of heavy cannabis smoking during adolescence – a period where the mind and brain are still developing.  Importantly, the authors conclude that prevention or delay of cannabis use is likely to have broad health and social benefits. This study is all the more timely, given the international debate on the legal status of cannabis use, as there is some provisional evidence to suggest that decriminalization and legalization may be associated with an increase in cannabis use during adolescence.

“There is some evidence to suggest that cannabis dependence may be on the rise. Across Europe, for example, cannabis is now second only to heroin as the main illicit drug taken by patients attending specialist addictions clinics.  It’s therefore imperative for us to understand the effects of cannabis.  Our team, led by Dr Oliver Howes, has previously found that heavy regular cannabis use is associated with a lowering of the brain chemical dopamine. Taken together, these findings tell us more about how cannabis affects the brain and the mind. This is essential in order for us to understand how cannabis increases the risk of mental illnesses and so that scientists can provide evidence to the public and policy makers on the strategies needed to reduce the potential harms associated with the drug.”

Prof Sir Robin Murray, Professor of Psychiatric Research, King’s College London’s Institute of Psychiatry, Psychology & Neuroscience (IoPPN) said:

“This is a careful study which puts together separate studies to get sufficient statistical power to investigate the effect of adolescent cannabis use on a range of outcomes. The authors conclude that daily use of cannabis before age 17 is associated with lower rates of high school completion and university qualifications, and increased risk of cannabis dependence, use of other illicit drugs, and attempted suicide.  None of the findings will surprise mental health workers, and indeed previous studies have reported similar findings for each of the outcomes separately. However, no study has examined these outcomes together or so carefully excluded possible artefacts.

“There is one important omission in the study – it does not provide data on the important question of whether the use of high potency cannabis is especially risky.

“This study reminds us that it is important to discourage cannabis use among teenagers, and that educational campaigns outlining the risks of heavy cannabis use are warranted whatever the legal status of cannabis.”

Prof David Nutt, Ex-President of the European College of Neuropsychopharmacology, said:

“This paper shows that heavy cannabis use is associated with poor social educational and mental health outcomes. This is not really surprising – it’s quite probable that the same would be true for heavy use of any intoxicating drug, perhaps even nicotine.

“The most interesting comparison would be with alcohol used in the same ways. In all cases it is likely that significant proportions of the users have pre-existing problems and seek cannabis as a way out.

“Another interesting comparison would be with the consequences of criminalisation for drug possession on the same educational and mental health outcomes – indeed was this taken into account?

“These data don’t really help with the legalisation debate as it’s been legal in Holland for decades with little impact – indeed young people may use less once it’s legal if they were rebelling by using it.”

Dr Adam Winstock, Founder of Global Drug Survey, Consultant Psychiatrist & Addiction Medicine Specialist, said:

“This is an important paper. It has combined the available research to highlight the risks cannabis use poses to young people. That the risks are greatest for those already most disadvantaged by poor mental health and educational engagement also reminds us that we should not respond to drug use in isolation of broader societal issues such as poverty and familial disintegration.

“The early onset of cannabis use is a potentially avoidable variable that compounds difficulties faced by those already most disadvantaged through socioeconomic deprivation and restricted educational achievement.

“Policies and credible messaging that delay the onset of cannabis and other drugs, including alcohol, till after 18 years old are desperately needed.”

‘Young adult sequelae of adolescent cannabis use: an integrative analysis’ by Sillins et al. published in The Lancet Psychiatry on Wednesday 10^th  September. 

Declared interests

None declared