Study: Marijuana caused more damage to teens’ brains than alcohol

Study: Marijuana caused more damage to teens’ brains than alcohol

(USA TODAY) — Marijuana use may pose a greater risk to the developing brains of teenagers than alcohol consumption, according to a new study this week.

The analysis, published Wednesday in the American Journal of Psychiatry, found that cannabis had greater short and long-term consequences than alcohol on four key components of teens’ memory. The finding greatly surprised researchers.

“We initially suspected alcohol would have a bigger effect,” Patricia Conrod, lead author and professor of psychiatry at the University of Montreal told USA TODAY.

Researchers looked at four cognitive functions: Problem solving, long-term memory, short-term memory manipulation and the ability to stop a habitual behavior when needed. Marijuana had “significant” negative effects on all four, while the study could not tie alcohol to negative effects, Conrod said.

However, alcohol’s effects may be greater as teens drink more later in life, Conrod said.

Authors examined nearly 4,000 students in the Montreal region over four years, starting when the average participant was about 13 years old.

The students took yearly memory tests and self-reported their alcohol and marijuana use. Those reports were kept confidential “unless such information indicated imminent risk of harm,” authors wrote.

By the fourth year, three-quarters of the students had consumed alcohol at least occasionally, while only about 30 percent of participants had used marijuana. But the study observed more daily marijuana users than alcohol users, Conrod said.

The study found some of marijuana’s negative effects were short-term, while others were lasting.

A particularly troubling finding: Young cannabis users may cause long-term damage to a brain function associated with substance abuse.

When studying response inhibition — that’s an individual’s ability to change their actions to help meet a goal — researchers found that teens using marijuana caused long-term damage to their brains.

Conrod said that finding may help explain a previously “perplexing” phenomenon: Young cannabis users have been shown to be at a greater risk for addiction later in life.


No posts to display


  1. You people will try everything to keep marijuana illegal. You will post a study that's framed in a very demeaning manner and give no input.

    Firstly, It doesn't "DAMAGE" the brain as stated and that's almost entirely based on the individual and whilst it does cause short term memory loss there is no conclusive evidence that it does damage to long term memory. Most of us smoke weed to forget the BS we go though some days anyways and there is nothing wrong with that, just as some take painkillers to stop headaches, some take pills to sleep or pills to slow them down/speed up.

    Secondly Marijuana does affect the part of the brain that deals with substance abuse but not in the way its framed in this article. Many clinics use cannabis to get people off harder drugs like crack, meth and opioids because of that effect it has.

    I suggest when you post an article you actually do a little reading into what your posting instead of playing puppet for people who want to keep weed illegal to push their own agendas and keep people swallowing pharmaceuticals like water.

    A better article to write about would be why we shouldn't blend marijuana with cigarettes or other narcotics because they are what actually do damage to our bodies and brains. Weed is supposed to be consumed on its own or with other herbs, NOT chemicals/drugs. You are the press, educate people instead of spreading nonsense.


  2. This is not the scientific consensus.

    In fact teen drinkers who also smoke cannabis may suffer less brain damage than teen drinkers who do not smoke cannabis:

    "Results confirm previous studies linking adolescent heavy drinking to reduced verbal learning and memory performance. However, this relationship is not seen in adolescents with similar levels of alcohol involvement who also are heavy users of marijuana."
    [Mahmood et al. Learning and memory performances in adolescent users of alcohol and marijuana: interactive effects. J Stud Alcohol Drugs. 2010.]

    "Teens reporting binge drinking behaviors alone had significantly lower FA than controls in all eight clusters, whereas teens reporting both binge drinking and marijuana use had lower FA than controls in only three of the eight clusters."
    [Jacobus et al. White Matter Integrity in Adolescents with Histories of Marijuana Use and Binge Drinking. Neurotoxicology and Teratology. 2009.]

    Even the U.S. Government has a patent on the cannabinoids found in cannabis for protecting the brain:

    "This new found property makes cannabinoids useful in the treatment and prophylaxis of wide variety of oxidation associated diseases, such as ischemic, age-related, inflammatory and autoimmune diseases. The cannabinoids are found to have particular application as neuroprotectants, for example in limiting neurological damage following ischemic insults, such as stroke and trauma, or in the treatment of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease and HIV dementia."
    [Patent 6630507 - Cannabinoids as antioxidants and neuroprotectants. Filing date: Apr 21, 1999.]

    In this study, researchers observed teens brains over a 1.5 year period. They found that teens who used alcohol during this period had reduced white matter integrity. These changes were not observed in cannabis users:

    "More alcohol use during the interscan interval predicted higher mean diffusivity (i.e., worsened integrity) in right and left superior longitudinal fasciculi, above and beyond baseline values in these bundles. Marijuana use during the interscan interval did not predict change over time."
    [Bava et al. Longitudinal changes in white matter integrity among adolescent substance users. Alcohol Clin Exp Res. 2013.]

    That said, there are concerns about regular, heavy teen use and adverse effect on the brain. As it stands over 80% of high school seniors report cannabis easy to get. This has remained unchanged for the last 30 years. Putting it behind the counter where merchants will actually check ID can actually reduce the regular, unfettered access that they have now. Regardless, criminalizing adults for something that children should not have is not rational or consistent with our legal system.


  3. Legalise the damn herb. Let those who will use it, wind up in the madhouse, dead as most would as roadkill, or rot in jail.


Comments are closed.