Ending Addiction for Good

Studies Show Long-Term Effects of Cannabis on the Brain

Cannabis has proven to be both damaging and addictive in two recent studies.

With the legalization of recreational marijuana in Washington and Colorado, questions about cannabis have vaulted into the public consciousness. For a couple minutes, let’s put aside policy concerns and look just at the effects of cannabis in the brain. Two studies published in top journals, both in April 2014, look inside human brains at the long-term effects of cannabis use. Is cannabis addictive? Is it safe? Let’s consider the evidence.

First, an article in the Journal of Neuroscience used MRI scans to look inside the brains of young, recreational marijuana users at regions associated with addiction. Previous studies have shown that other drugs known to be addictive affect the brain’s reward centers – especially the brain’s amygdala, which controls emotional learning, and a structure called the nucleus accumbens, which controls pleasure (including our ability to laugh). We’ve also known that adding cannabis-based chemicals to the brains of rats creates changes in these structures related to addiction. But it’s quite a leap from introducing cannabinoids to rat brains and knowing the effects of smoking pot on humans.

So a team of Harvard-led researchers recruited 40 young adults – 20 marijuana users and 20 non-users – to see if what is true in the brains of rats is also true in the brains of college students. Sure enough, human marijuana users had changes in volume, density and topography in both of the amygdala and nucleus accumbens.

“These data suggest that marijuana exposure, even in young recreational users, is associated with exposure-dependent alterations of the neural matrix of core reward structures,” the researchers write.

This study and the studies that lead up to it show that marijuana use creates physical changes in the brain associated with addiction. And, the researchers point out, these results were seen in non-dependent, young adult users. What are the effects of even heavier pot use on the brain?

That’s the question of the second study, published in the Nature journal, Neuropsychopharmacology. Again, the study used MRI imaging to ask if the effects of cannabis-based chemicals seen in rat brains are also seen in human brains. This time the study compared heavy marijuana smokers to occasional smokers to see if overall brain changes are more extreme, the more you smoke. And it looked outside just the structures of addiction to explore changes in overall brain structures: how does marijuana use affect the brain?

The study found reduced grey matter volume in nearly all brain regions that are rich in the “receptors” that can trap and respond to cannabis-based chemicals. These regions include a long list of structures, almost all of which are part of a network that controls motivation, emotion, and emotional learning. Here’s an important part: the degree to which these brain areas changed was due to one of two things – either heavy use or starting use during adolescence. Long-term heavy users had the same reductions in grey matter volume as lighter users who started in their teens.

So let’s revisit our two questions. Is marijuana addictive? Yes, and a real, visible change in the brain’s reward system. And is marijuana safe? No, and the younger you start or the more you use over time, the more dangerous it is to your brain. Whether or not you believe recreational marijuana should be legal, it’s time to admit its power as a dangerous, addictive drug.


Richard Taite is founder and CEO of Cliffside Malibu, offering evidence-based, individualized addiction treatment based on the Stages of Change model. He is also co-author with Constance Scharff of the book Ending Addiction for Good.

I would like more detailed information please...

The study may show long-term effects of cannibis use but this article doesn't. We're not all neuroscientists so we are not going to further investigate and download this study to read more about it. So why not state the specific symtoms of having reduced gray matter from cannibis use? Why does this article not give details?

Also the study should correleate the reduced brain matter with tests of psychological health of the individual, relationship health, and proffesional occupation. I wish the scientests furthered their research but that might be too much work for whoever is funding this binary study. Either way this article has too little information. I love studies and articles but this one makes no effort to explain the real-world daily life implications of having your gray matter reduced by cannabis use. It's just internet fluff trying to get view counts.

Gosh, a treatment provider who

interprets heavily criticized "studies" that support his profession. Hoodathunk?

Logic and Good Studies

I'm not a marijuana proponent but both these studies are limiting at best. While the study appears conclusive on the surface, it falls very short in the long run. In the full article the authors state a causative relationship between the cannabis use and the anatomic changes throughout the article, only to state in the second-to-last paragraph that no causative relationship can be concluded.
A plausible alternative interpretation of this data is that the neuroanatomical abnormalities predate the drug use and make the individuals more likely to use cannabis. By reversing the causative relationship here, we would suppose that greater anatomical changes would cause increased consumption.
As noted, there is evidence showing an empirical link between tetrahydrocannabinol administration and neuroanatomical changes in rodents not humans.
A causative relationship based solely on this abundantly flawed 20 person group study is simply not present.

A question about duration

From the article and the studies I'm unable to tell whether or not the neuroanatomical changes were observed straight after the application of the cannabinoids or after some time without use. When speaking of long term effects, I would think it an important piece of information to know whether the effects last even after use of the drug has ceased and as cmw stated, whether or not the abnormalities existed before the post use tests.

More Marijuana facts

Marijuana oil cures 25 out of 26 stage 4 cancer
But it might be money well-spent. All 26 of Finley's referrals had stage 4 cancers -- brain tumors, colon cancers, lung cancers -- which means the malignant growths had metastasized to other organs. Most had prognoses of a few months to live, some had less than six weeks. All complemented modern Western medicine treatments such as chemotherapy with the concentrated oil -- and all but one have survived, she says. A patient's prognosis can very widely depending on the type of cancer, but the disease is a reliable killer at stage 4, meaning Finley's patients' 96 percent survival rate is unheard-of.

"I'm not a stoner," she says now, almost defensively, noting that classmates at Oakland-based cannabis grow college Oaksterdam University, where she honed her cultivator skills, at times mistook her for an undercover cop. "It was against my own prejudice that this could really be true."

These survival stories are becoming more common. One of the most high-profile was the case of Montana toddler Cash Hyde, diagnosed with a brain tumor at 20 months, whose family credits cannabis oil for keeping the tumor at bay and keeping him alive -- until a change in Montana state law cut off his access to oil for a few months. The tumor returned and he died in November, at age four.

These stories are remarkable, but for now they're also just stories -- which means they're all but worthless to the medical community, which needs hard data. "Anecdotes are not evidence -- you need to do research, controlled studies," says Dr. Donald Abrams, the chief of oncology at San Francisco General Hospital and an integrative medicine specialist at the University of California at San Francisco. Abrams, a personal friend of the Aldriches who has researched cannabis's medical value extensively -- and is a believer in its value -- is still a scientific skeptic. "I hear stories all the time -- 'I was cured of cancer by this or that' -- and most of the time it's frankly bogus." We need to stand up and revolt. The state of Montana murdered that child. How much longer are you going to allow this government to control us. I refuse to ask the government for the right to use marijuana. I got arrested once for possession but I didn't know all this at the time. No cop will ever take it from me again and if he tries he wants to have a army backing him up. The government is a murderer why shouldn't they be killed. They killed that little child.

Great article I'm glad this

Great article I'm glad this has come out. I live in a street with lots of older guys who've been smoking pot heavily for years , it takes them years to do anything that would take anyone else a few days & the job is done poorly if it's ever finished. They also don't seem to be able to tell the difference between junk & something valuable or a stupid idea from a brilliant one. There also seems to be a theatricality about what they do, they want attention for their pathetic antics.

I used to like the neighborhood because I was a heavy drinker, they provided excellent "cover" but after reading the remarkable book "Willpower. Rediscovering the Greatest Human Strength" (by Baumeister & Tierney) I quit, didn't even even read the book in order to quit. Now I'm thinking what the hell am I doing here?!

I think addiction is symptomatic of our societies emphasis on self-esteem & how one feels over self-control and how things actually are, drugs make things seem good and make you feel good about yourself but they're actually making both worse.

But I think 'well- adjusted' people are just as likely to be addicted to consumerism in the same way, they're busy destroying the planet to feel good with the latest mindless purchase, perhaps they're worse than the pot-heads?


Thank-you for your article. It's wonderful to hear some sense in this debate. I fear people will find out the hard way, say 20 years from now, that you and the studies are right.

And if smoking tobacco, with all the burnt particles, is bad for the lungs, why wouldn't smoking marijuana also be bad!


A lot of people feel threatened by marijuana. We all tend to fear the unknown. Marijuana does not have to be smoked. I prefer vaporizing or eating it myself. I don't know why people feel threatened because if you have drank milk you have had THC already. THC is found in all breast milk and if it wasn't your baby would stand a far greater chance of dying. Marijuana has over 60 something cannabinoids that we know of as of date. Most have not been researched except THC and CBD. There is little known about CBN or CBC or all the others. It is a fantastic help for insomnia it cures sleep apnea and is excellent in many neurological disorders. I got up one morning and my blood pressure was 146 over something. I told my wife watch this and I went and smoked a bowl. In just 10 minutes my top number dropped to 115 from the 146. There are thingsI don't care for like short term memory but what it has done for my insomnia is nothing short of incredible. My insomnia is so bad with no meds I am lucky to get 1 hour of sleep per night. I was taking extremely high dosages of sleeping meds just to get to sleep. The meds would have killed me I am positive. Now I take no meds and I get 7 to 10 hours of sleep per night. I have a lot of PTSD because of my childhood and that is almost gone now. Ingesting oils is the best way because I do believe smoking it will be harmful. Vaporizing is also great. It also helps my wifes Parkinson's Disease with her leg tremors. It stops them completely. Like I said unless you didn't drink milk everybody has had THC.

The issue is not whether or

The issue is not whether or not cannabinoids show promise as medicine. There is plenty of evidence of that and we’d like to see more research in that area so that marijuana is applied and used in the best and safest ways possible. Where we are concerned is with young people, under the age of 25, using marijuana recreationally. There is significant research that shows that marijuana use significantly impacts brain development in this population. It is young people who need to be educated about the long-lasting effects of recreational marijuana use so that they can make sound choices. This is no different than educating young people about the dangers of smoking tobacco or drinking and driving.

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Richard Taite is CEO and founder of the Cliffside Malibu Treatment Center in Malibu, California and co-author of the book Ending Addiction for Good.


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