Safe cannabis notion ‘misplaced’
Tuesday 27th August 2013, 2:51PM BST.
Teenage brains may be especially vulnerable to the harmful effects of cannabis, experts believe.
The notion that cannabis is a “safe” drug is misplaced and scientifically inaccurate, say researchers.
Scientists came to the conclusion after reviewing more than 120 studies looking at the effects of cannabis on the adolescent brain.
Professor Didier Jutras-Aswad, from the University of Montreal in Canada, who led the team, said: “Data from epidemiological studies have repeatedly shown an association between cannabis use and subsequent addiction to heavy drugs and psychosis.
“Interestingly, the risk to develop such disorders after cannabis exposure is not the same for all individuals and is correlated with genetic factors, the intensity of cannabis use and the age at which it occurs.
“When the first exposure occurs in younger versus older adolescents, the impact of cannabis seems to be worse in regard to many outcomes such as mental health, education attainment, delinquency and ability to conform to adult role.”
Rat experiments had shown how cannabis targets areas of the brain linked to motivation, decision-making and habit-forming that change rapidly during the teenage years.
Taking the drug at this stage in life could greatly affect development of the brain and personality, according to the scientists writing in the journal Neuropharmacology.
“Of the illicit drugs, cannabis is most used by teenagers since it is perceived by many to be of little harm,” said Prof Jutras-Aswad.
“This perception has led to a growing number of states approving its legalisation and increased accessibility.
“Most of the debates and ensuing policies regarding cannabis were done without consideration of its impact on one of the most vulnerable population, namely teens, or without consideration of scientiﬁc data.
“While it is clear that more systematic scientiﬁc studies are needed to understand the long-term impact of adolescent cannabis exposure on brain and behaviour, the current evidence suggests that it has a far-reaching inﬂuence on adult addictive behaviours particularly for certain subsets of vulnerable individuals.”
Some people are genetically more susceptible than others to becoming dependent on cannabis, the research suggests.
In adolescent rats, scientists had observed individual differences in the chemical pathways that govern addiction and vulnerability.
This may help explain why around a quarter of teenager cannabis users end up abusing the drug or developing a dependency.
Studies also indicate that cannabis dependence can be inherited through certain genes passed by parents to their children. Psychological influences are another important factor, say the researchers.
“Individuals who will develop cannabis dependence generally report a temperament characterised by negative affect, aggressivity and impulsivity, from an early age,” said Prof Jutras-Aswad.
“Some of these traits are often exacerbated with years of cannabis use, which suggests that users become trapped in a vicious cycle of self-medication, which in turn becomes a dependence.”
He added: “It is now clear from the scientific data that cannabis is not harmless to the adolescent brain, specifically those who are most vulnerable from a genetic or psychological standpoint.
“Identifying these vulnerable adolescents, including through genetic or psychological screening, may be critical for prevention and early intervention of addiction and psychiatric disorders related to cannabis use.
“The objective is not to fuel the debate about whether cannabis is good or bad, but instead to identify those individuals who might most suffer from its deleterious effects and provide adequate measures to prevent this risk.”
Co-author Dr Yasmin Hurd, from the Icahn School of Medicine at Mount Sinai, New York, said: ” Continuing research should be performed to inform public policy in this area.
“Without such systematic, evidenced-based research to understand the long-term effects of cannabis on the developing brain, not only the legal status of cannabis will be determined on uncertain ground, but we will not be able to innovate effective treatments such as the medicinal use of cannabis plant components that might be beneficial for treating specific disorders.”