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Fifty-Year Study "Concludes" Long-Term Cannabis Use Leads to Violent Behavior

  1. Beenthere2Hippie
    View attachment 49502 New research published online in advance of print in the journal Psychological Medicine, concludes that continued use of cannabis causes violent behavior as a direct result of changes in brain function that are caused by smoking weed over many years.

    Researchers have long debated a possible link between use of marijuana and violent crime. In contrast to alcohol, meth, and many other illegal drugs, the mellowing effects of cannabis seem unsuited to promoting violent behavior. However, ample previous research has linked marijuana use to increased violent behavior. The sticky problem in such studies are the many confounding factors involved in interpreting this correlation.

    It is very difficult to determine whether any statistical correlation between marijuana use and violent behavior are causally linked, or instead the two are associated through some other factor, such as socioeconomic status, personality traits, or many other variables that are related to the propensity to use marijuana. Moreover, the causal relation between smoking pot and violent behavior could be in exactly the opposite direction. That is, individuals who are involved in violence or who commit criminal offenses may also be people who are more open to using marijuana.

    After all, marijuana is an illegal substance in most places, so people with antisocial personality traits and those with tendencies toward lawlessness may be the type of individuals inclined to be more open to obtaining and using the illegal substance. Not so, conclude neuroscientist Tabea Schoeler at Kings College London, and her colleagues, "Together, the results of the present study provide support for a causal relationship between exposure to cannabis and subsequent violent outcomes across a major part of the lifespan." Let's examine the evidence provided by this new study.

    What makes this new study more compelling than previous studies is that the researchers followed the same individuals for over 50 years from a young age to adulthood. This is precisely what one needs to solve the chicken or egg riddle with respect to cannabis and violence: just look and see which one happens first.

    These subjects were in the Cambridge Study in Delinquent Development, comprised of 411 boys who were born around 1953 and living in working-class urban neighborhoods of London. 97% of them were Caucasian and all of them were raised in two-parent households.

    The researchers took into consideration other factors, including antisocial traits as assessed by the Antisocial Personality Scale, alcohol use, other drug use, cigarette smoking, mental illnesses, and family history.

    Hers's what they found: Most of the participants never used cannabis and they were never reported to have violent behavior. 38% of the participants did try cannabis at least once in their life. Most of them experimented with cannabis in their teens, but then stopped using it. However, 20% of the boys who started using pot by age 18 continued to use it through middle age (32-48 years).

    One fifth of those who were pot smokers (22%) reported violent behavior that began after beginning to use cannabis, whereas only 0.3% reported violence before using weed. Continued use of cannabis over the life-time of the study was the strongest predictor of violent convictions, even when the other factors that contribute to violent behavior were considered in the statistical analysis.

    In conclusion, the results show that continued cannabis use is associated with a 7-fold greater odds for subsequent commission of violent crimes. This level of risk is similar to the increased risk of lung cancer from smoking cigarettes over a similar duration (40 years). The authors suggest that impairments in neurological circuits controlling behavior may underlie impulsive, violent behavior, as a result of cannabis altering the normal neural functioning in the ventrolateral prefrontal cortex.

    R. Douglas Fields, Ph.D., is a neuroscientist and author. His experimental research focuses on the cellular mechanisms that regulate nervous system development and learning according to functional activity. This includes both the involvement of neurons and non-neuronal cells (glia) in brain function and plasticity. He is Adjunct Professor at the Neuroscience and Cognitive Sciences at the University of Maryland, College Park.

    By Dr. R. Douglas Fields - Psychology Today/March 20, 2016
    Art:1- posterposse; 2-miamiartguide
    Newshawk Crew

    Author Bio

    BT2H is a retired news editor and writer from the NYC area who, for health reasons, retired to a southern US state early, and where BT2H continues to write and to post drug-related news to DF.


  1. Beenthere2Hippie
    I could not disagree more with what is stated in this study, based on my own personal experience of multiple decades of recreational cannabis use. I call complete and utter bullshit on this study, and suggest that somewhere in the phase of data analogy someone dropped the ball. In fact, maybe multiples balls. I have no idea of the hows of that happening, but the "whys" seems more than obvious, considering the direction many in the western world would like cannabis acceptance by enlightened society to take on the entire subject.

    As for me, I am highly disappointed that a magazine touting the quality reputation of Psychology Today would rise to such a new low and publish such drivel. So I've chosen to share this important "study," since many of us will be hearing about this latest nonsense propaganda sometime in the near future from people who want to believe any and all negative theories or studies they hear about on marijuana.

    The war on drugs continues--even on well-established, long-accepted-as-harmless substances, such as weed.
  2. Alfa
    So they followed 31 pot smokers for 50 years and 7 of them reported that violent behavior started after pot smoking. And this is proofs anything?

    How about simply getting country wide incident data and check how many pot related incidents have been reported? Surely if pot would have caused violent behavior then something would show up on such a large scale. But it doesn't. On average 4% of the population of most countries smoke pot. That's significant enough to measure on a large scale and to tie it to national and international statistics.

    This is not the first overreaching conclusion on drugs from King College in recent years.
  3. Waiting For The Fall
    "Most of the participants never used cannabis and they were never reported to have violent behavior." Almost two-thirds of the participants--those who didn't use cannabis--never reported having violent behavior? I find that incredibly hard to digest.

    Psychology Today, et al, should also publish information regarding which corporations have given grants to these researchers to fund these sloppy papers, bereft of solid information.
  4. aemetha
    This isn't a study, it's a survey. Surveys have a place, they indicate places for us to study but drawing conclusions based on a survey neglects the most important part of scientific discovery... evidence of causality.

    It's shameful that a person with the word scientist in his job title has so completely abandoned the Socratic method. Why spend so many years on a neuroscience degree to perform work a high school stats student could have done.
  5. vervain
    Haha, isn't King's College the one who also published the recent study blaming "Skunk-Like" cannabis for brain damage, using that term like it was some kind of biological classification? Forgive me if I roll my eyes a little. And unless there's some major facets and controls for this newer "study" omitted by the article, it's the opposite of scientifically rigorous.

    And of course for anyone that's actually smoked pot the claim is ludicrous. Now, if they'd said imbibing cannabis was responsible for an increased incidence of watching bad comedy movies and eating chips & salsa, I'd agree they just might be onto something...
  6. detoxin momma
    ^^^^ hahaha , yeah i agree with vervain...binge eating, does that count as violent behavior,lol...

    if you take 50 people all using any substance surely 7 of them would be prone to violent behavior.

    i bet if you took 50 pot smokers, then took their pot away, the number would increase drastically.
  7. lololsolid
    The only violent behavior I've ever demonstrated when baked is violence towards my weight by eating too much.

    That being said, it's also "possible", though I would guess unlikely, that the story has some merit. One must consider our own biases, having found this "survey/study" through a site where the common denominator between all of us is drugs. We're biased too, likely against the evidence that smoking weed could be bad for you.

    Despite the findings of the study, I will continue to toke when I feel like it and receive A+'s in the science courses I'm enrolled in. So much for the other "study" my one professor has plastered on his door that compares the brain damage from chronic meth abuse to that of marijuana smokers. Little does he know, the guy breaking the curve in his class has been smoking weed almost every day for 6 years and takes LSD+MDMA twice-four times a year.

    It is abysmal, in my opinion, how little research is actually done on the huge epidemic that is drug abuse. Instead, I see a bunch of garbage about how we need to bomb ISIS. I quote from an article with the source linked below, "Drug use is on the rise in this country and 23.5 million Americans are addicted to alcohol and drugs. That’s approximately one in every 10 Americans over the age of 12 – roughly equal to the entire population of Texas. But only 11 percent of those with an addiction receive treatment. It is staggering and unacceptable that so many Americans are living with an untreated chronic disease and cannot access treatment" - Dr. Kima Joy Taylor, director of the CATG Initiative. <http://www.drugfree.org/new-data-show-millions-of-americans-with-alcohol-and-drug-addiction-could-benefit-from-health-care-r/>

    Where's the research on how to break addiction? Are a few thousand deaths via terror attacks over the last decades more important than the socio-economic impact of over 23 million American addicts? Where the FUCK is the logic in that?
  8. Calliope
    I don't know why we need to be so immediately convinced there is not any link between long term cannabis use, especially initiated from a very young age, and subsequent violence. Such a link wouldn't mean everyone who uses cannabis gets violent at all. And it wouldn't mean other drugs (one thinks of alcohol and various stimulants of course) don't have an even stronger link especially one associated with acute use that materializes while high on the substance itself. That may not be the case with cannabis at all. Stoned people do tend to be more mellow than hair-trigger set to go off. But christ knows I've had to deal with a fair number of angry cannabis abusing males in my life. And yes sometimes they got violent. Why assume a psychoactive like cannabis used over long periods won't cause any erosion of inhibitions and perhaps disregulate of mood states in ways that might increase the likelihood of violence?

    The actual study this story discusses is not as ridiculously full of bad scientific method as posts in this thread claim. The study is in the DF archive now here: T. Schoeler, D. Theobald, J.-B. Pingault, D. P. Farrington, W. G. Jennings, A. R. Piquero, J. W. Coid and S. Bhatt. Continuity of cannabis use and violent offending over the life course (2016) Psychological Medicine. published online ahead of print March 2016

    The study was of a cohort of more than 400 males, not 7; their analysis did pay attention to potential confounding factors; and the measures of violence were in fact not simply self-report but also a review of 46 years of criminal convictions for robbery, assault, threatening behaviour or possessing an offensive weapon.

    And they don't make the claim the pretty shoddy Psychology Today piece apparently hallucinated after doing some hot knives or something. They say their results are consistent with but cannot establish a causal relation. It behooves us to read these things I think before getting into a defensive frenzy of outrage. The strongest thing they say about long-term cannabis use leading to violence is,

    It has also been reported that the strength of association between crime and cannabis varies across different developmental stages in adolescence, with younger users being more affected than older users (Fergusson et al. 2002), again suggesting that a range of associated psychosocial risk factors evident in younger cannabis users may increase its effect on violence... Although the findings indicate pharmacological effects of cannabis on violence, the relatively long lag between the measurement time points (>12 years in structural equation models) do not allow one to draw conclusions regarding acute or non-acute pharmacological effects. Nevertheless, the findings are consistent with independent experimental evidence that a single dose of cannabis can cause impairments in behavioural control that may underlie impulsive, violent behaviour, by altering the normal functioning of its underlying neural substrate, the ventrolateral prefrontal cortex in man (Bhattacharyya et al. 2014). ​

    And overall they say,

    Together, these results imply a reciprocal relationship between cannabis use and violence, which is consistent with a number of studies that reported such a relationship between substance use and violence in adolescence and emerging adulthood (Xue et al. 2009; Scholes-Balog et al. 2013) as well as studies that suggest a link between impulsiveness/disinhibition or conduct problems evident in childhood and subsequent use/ abuse of cannabis (von Sydow et al. 2002; Brook et al. 2013; Pingault et al. 2013), alcohol (Caspi et al. 1996) or illicit drugs (Fergusson et al. 2008). Our results tend to suggest that these reciprocal effects are only dominant in early adulthood and violence in later life is not associated with subsequent cannabis use, although cannabis use at later age remained a significant predictor for SR-V [self-reported violence]. ​
  9. aemetha
    I think it absolutely warrants further research, as does any statistical analysis that identifies a potential health issue. My problem with it (and to be fair this is based on my experience of other reported statistic based claims) is that they too often jump from identifying a potential issue to implementing solutions to that issue, without fully understanding the cause. This causes a great deal of misinformation and solutions are less effective.
  10. Beenthere2Hippie
    The results, then, do not ring true. I'm sure I'm not alone in feeling that way about this study, and that I am not the only one here who is more than skeptical of a study claiming cannabis leads anyone to become violent - unless, of course, they are seriously violent by nature to begin with. But even then, it's hard to believe smoking weed would make even that person more violent.

    I'm more than curious what others will think of what you've found, Calli. Thank you either way, though, for sharing the information you uncovered. I am by no means trying to shoot the messenger :eek:. I just find this study beyond impossible to take seriously. But who knows what more opinions will shed light on.
  11. Fentiful
    I figured I'd offer my two cents. I started using/abusing cannabis at an early age, around 15. In a short time I became "addicted", and was smoking between a quarter to a half ounce a day. While I will say that like others, while on it, I was mellow, relaxed, calm, if not paranoid and anxious at times, during the "come down" when I would generally want to do nothing but sleep if I wasn't going to continue to "party" with more marijuana and/or other substances, I was a lot more prone and susceptible to violent outbursts and actions.

    While I do acknowledge underlying mental health issues, such as depression, low self esteem, unresolved anger due to external circumstances going on in my life, some pretty traumatic during a crucial time in my development, I believe it was my drug use that often times pushed me over the "edge". My own experience also correlates with the studies stating that marijuana use during an individuals teenage years, a time crucial to neurological development, caused "brain damage", resulting in aggravated and new mental "disorders". I had a brother as well who engaged in similar drug use habits who would act the same way when "coming down", and after I'd gotten off of it, I could always tell when he was using, if by this behavior as well. We were always much more likely to get into arguments when he was coming down and or hadn't had any for a spell.

    After I quit my addiction to cannabis, which ultimately was brought about by the fact that I would have a panic attack almost every time I got high, and about a year later, I a lot of the mental distress and issues I had cleared up, with no therapy or counseling or other subsequent medications or self medicating.

    I wouldn't be so quick to address this study out of hand, while it doesn't site a huge increase in the general population who become violent from marijuana use, it is something that should be looked at more, and considered, especially cannabis use in teenagers and young adults. I think often times users or pro-cannabis folks consider how a person acts while under the influence or at the peak of their high, and perhaps not the bigger picture. Not only that, but every persons neurochemistry and biology is unique and different people react differently to different substances, and the same person can react or act different each time they use, even if it is the same substance.

    I don't have an agenda, I'm not pro or against cannabis use, by and large, except in under age individuals and addicts, (and yes, I do believe from personal experience and as a witness, that one CAN be addicted physically and mentally to cannabis!), I just figured I'd offer up my own experiences.

    Not that long ago, I revisted it's use, strictly for chronic pain purposes after abstaining from it for over 10 yrs. While I did not experience anxiety and paranoia, most likely because I highly moderated my use and was experimenting with it for pain purposes, however I did not find it to be beneficial to me physically or mentally. I did not like the "cloudiness" of mind it provided, while at the same time, seemingly amplifying my pain. While I'm aware of the various strains and possible benefits, especially given the fact that I was diagnosed with cancer a little over a year ago, I find other things to provide much better pain management and help with nausea, without the bothersome side effects.

    My two cents,
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