Pot Smoking Could Leave Lasting Neurological Impression On Teenagers
    By News Staff | December 17th 2009 12:00 AM | 3 comments | Print | E-mail | Track Comments
    The potentially damaging effects of marijuana on young brains may be even worse than previously thought, according to new research conducted by scientists from McGill University. Their new study, published in Neurobiology of Disease, suggests that teenagers who consume marijuana daily face a higher risk of depression and anxiety, and may suffer irreversible neurological effects.

    "We wanted to know what happens in the brains of teenagers when they use cannabis and whether they are more susceptible to its neurological effects than adults," explained McGill University researcher Gabriella Gobbi.

    The study points to an apparent action of cannabis on two important compounds in the brain – serotonin and norepinephrine – which are involved in the regulation of neurological functions such as mood control and anxiety.

    "Teenagers who are exposed to cannabis have decreased serotonin transmission, which leads to mood disorders, as well as increased norepinephrine transmission, which leads to greater long-term susceptibility to stress," Dr. Gobbi stated.

    While previous epidemiological studies have shown how cannabis consumption can affect behavior in some teenagers, "our study is one of the first to focus on the neurobiological mechanisms at the root of this influence of cannabis on depression and anxiety in adolescents,"  Dr. Gobbi claimed. It is also the first study to demonstrate that cannabis consumption causes more serious damage during adolescence than adulthood.

    Citation: Francis Rodriguez Bambicoa, Nhu-Tram Nguyena, Noam Katza, Gabriella Gobbi, 'Chronic exposure to cannabinoids during adolescence but not during adulthood impairs emotional behaviour and monoaminergic neurotransmission', Neurobiology of Disease, Dec. 2009; doi:10.1016/j.nbd.2009.11.020


    Gerhard Adam
    Some important missing answers .... how long did this study take place?  What were the controls?  Was this "damage" observed when these teenagers became adults?  What determined that it was irreversible?  How does this compare to alcohol (as an example)?  What does "higher risk" mean based on this study?
    Mundus vult decipi
    This PR blurb is amazingly disingenuous. The study was done on adolescent rats, not humans, and did not even involve marijuana, but instead a synthetic marijuana analogue that has both a higher for CB1 receptors than marijuana does, and also happens to be structurally quite different.

    This isn't to say that theres anything wrong with rat studies, or that inferences can't be made from chemical analogues but to say that "y causes x" is an oversimplification that comes pretty close to just being deceitful.

    I go into a little more elaborate detail about this study at my blog at

    What is not mentioned in the news blurb was that the study involved RATS, not humans, and a SYNTHETIC cannabinoid, not real marijuana or even THC extract. Daily injections were used instead of smoking, and the doses used were fairly strong. And the adolescent rats could best be described as EARLY adolescent rats, and the adult rats can best be described as early adult rats.

    The headline should read as follows: "Chronic daily exposure of relatively strong doses of synthetic cannabinoids can leave lasting neurological impression on early adolescent rats." Because that is all the study actually proves, though far less "sexy" than this article's choice of a headline.