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Cannabis & Mental Illness: What Does the Research Say?

Cannabis & mental illness: What does the research have to say?

Cannabis—it’s a plant that’s well known for getting people high, but it’s also become increasingly accepted for medicinal purposes, particularly for pain and nausea. But what do we know about the interaction between cannabis and mental illness?

There’s been a clearly established link between cannabis use and triggering the onset of psychotic illness in people who are susceptible. When it comes to mood and anxiety disorders, there isn’t as much research.

Cannabis is now legal in Canada and a number of American states, and I suspect that one of the benefits of this is that there will likely be increased funding available for cannabis research.

The Canadian Institutes of Health Research, a government agency, currently has a competition open for grants to conduct cannabis research. The amount earmarked for mental health research is $4.5 million. Doing a quick search I wasn’t able to find an estimate of research dollars in the U.S.

Hopefully, in a few more years we’ll have a much better understanding of the science of cannabis. But here’s a brief look at what science can tell us now.

What’s in cannabis?

While Cannabis sativa plants contain more than 100 different types of cannabinoid elements, two in particular appear to be key in mediating the health effects of cannabis.

Delta-9-tetrahydrocannabinol (THC) is responsible for the psychoactive effect, or “high”, that cannabis produces. It also has analgesic and anti-nauseant effects.

Cannabidiol (CBD) is non-psychotomimetic, meaning it does not cause a “high”; in fact, it may even counteract that effect of THC. It’s being researched for potential use in a number of different health conditions, including epilepsy.

Both THC and CBD act on cannabinoid receptors in the brain, much like the body’s own natural endocannabinoids do. This is along the same lines of how opioids act on the body’s endogenous opioid receptors. As with opioids, the fact that these molecules act on endogenous receptors is not inherently a good or bad thing.

Endocannabinoid receptors

The endocannabinoid system involves two key receptors, CB1 and CB2, and influences a variety of cognitive processes including learning, memory, mood, sleep, and motivation.

The anti-obesity drug rimonabant acts as an antagonist at CB1 endocannabinoid receptors, and it can produce symptoms of depression and anxiety in individuals without mental illness. This suggests that decreased natural activity at endocannabinoid receptors can negatively impact serotonin signalling in the brain. One study found lower than normal concentrations of CB1 receptors in autopsies of the brains of depressed people.

THC is a CB1 and CB2 agonist. CBD boosts the activity of one of the body’s natural endocannabinoids and antagonizes the effects of THC.

Cannabis use and mental health

A statement by the National Academies of Science, Engineering, & Medicine found evidence of a number of mental health  effects associated with cannabis:

  • increased symptoms of mania and hypomania in people with bipolar disorder with regular cannabis use (moderate evidence)
  • small increase in the risk of developing depression (moderate evidence)
  • increased suicidal ideation, attempts, and completion (moderate evidence)
  • increased social anxiety disorder among regular users (moderate evidence)
  • There is no evidence indicating for or against an effect of cannabis on changes in symptoms or course of illness in people with depression
  • There is moderate evidence that depression is a major risk factor for developing cannabis abuse

According to Lev-Ran and colleagues., multiple large cross-sectional studies have demonstrated high rates of co-occurring cannabis use and depression, although that level of evidence is insufficient to make inferences around causation.

They found that cannabis use moderately increased the risk of developing depression, with a somewhat larger increase in risk associated with heavy cannabis use. Similar results were found in both adult and adolescent populations. The mechanism for this was unclear, and the authors suggested that it could be related to direct effects on cannabinoid receptors, or it could be mediated indirectly by psychosocial consequences of cannabis use.

A study by Agrawal et al. found that heavy cannabis use was associated with an increased incidence of depression and suicidal ideation. However, a study by Blanco and colleagues did not find a significant association between cannabis use and the development of depression.  A study by Schoeler et al. concluded that onset of cannabis use before age 18 was associated with an increased risk of developing MDD, but late-onset use (after age 27) was not.

Feingold et al. found that people with depression were more likely to start using cannabis, and the authors suggested this might e a form of self-medication.

What does this mean?

One of the benefits often ascribed to cannabis is that it’s a natural alternative to pharmaceuticals. However, the fact that a substance is plant-based rather than synthetic does not necessarily mean that the substance is either a) therapeutically effective, b) safe, or c) free of unwanted effects (i.e. side effects).  If cannabis has therapeutic benefits, that’s great, but for me, the “natural” argument in and of itself doesn’t hold water.  And with these findings, the biggest take-away message that I’m getting is that more research is needed.

Hopefully, with government research funding agencies offering more grant money for research into the effects of cannabis, we’ll have a clearer picture of how components the various components of cannabis affect mental health and mental illness.  It would be particularly interesting to see what potential role CBD might play.  Until the science is there to back it up, though, it’s probably not something that I’m going to be putting into my body.


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44 thoughts on “Cannabis & Mental Illness: What Does the Research Say?”

  1. I personally think there’s a lot of research to back up cannabis being beneficial towards people’ mental health, however it’s not for me. I used to smoke it a lot, but it just makes me anxious. However, there’s so many people I know who smoke it to calm their anxiety and depression down. I think it depends on the person. I do think people should stop shutting it down just because it’s an illegal drug. Alcohol was illegal once too, now people drink it all the time because it’s normalised. Cannabis, from my experience, is way less dangerous than alcohol. There’s a lot of people who have spoken up about cannabis helping them enormously with physical and mental health issues, so I don’t think they should be shut down and ignored just because the government has decided a plant is illegal. I’m going off on a bit of a tangent here so I’ll stop now! Haha. Really interesting post though – I haven’t seen much written about this topic on WordPress.

    1. Cannabis was legalized in Canada last year, and I thinkthat was a positive move. Prohibition hasn’t worked before with alcohol, and there’s really no reason to think it would be any different with cannabis.

  2. Synthetic drugs come from natural derivatives, so you’re right that that argument is somewhat flat. Marijuana has not been researched because of people’s negative views or stigmas toward it. Marijuana is a plant with leaves and a flower, so I’m into it. The “high” is different for anyone and I’m not a doctor, so I’m not prescribing. We need to now MORE, and we need to know more like, yesterday.

  3. In America if you have chronic pain

    I was in a triple rollover with damage to my cervical spine

    After fusions and nerve killings my pain was unbearable

    Chronic pain is a whole different animal

    So through workers compensation I had a PhD. Pain psychologist, neurosurgeon couple neurologist and two pain doctors

    I was in a chronic pain group

    15 of us met weekly

    The norm was maybe 19 yo 15 pills a day

    The strong opioids and anti anxiety pills dominated

    We were all over medicated and our pain pills lost power and side effects were numerous.

    I walked out of that group threw my pills away and substituted medical weed

    Since legalization the quality and cleaner products have emerged

    For us chronic pain sufferers weed has more than one benefit

    Nausea, vomiting and lack of appetite plague us

    Weed solves this problem and kills much of the pain

    I would be dead by now on the opioids and prescription drugs

    The side effects grew and those pills took my willpower

    It is a personal choice

  4. Very interesting. I’m looking into CBD oil for my chronic pain. I certainly don’t want anything else affecting my mental health.
    I used to smoke a lot, and I mean a lot of weed when I was in my late teens through late 20’s. It wasn’t until I experienced my first panic attack that ended me up in the hospital that I quit smoking.
    Thanks for sharing this… Again, I know to check with my general practitioner before taking cbd oil. Lord knows the psychiatrist wouldn’t say yes or no. She’s the one that prescribes my meds, and she couldn’t give me a yes or no answer? Wrong.

            1. This is just a guess but it’s probably approved as a dietary supplement, and I think some doctors feel like they don’t have enough information to recommend for or against something. Plus they don’t want to get sued if they said go ahead and use something and it had an unintended negative effect.

            2. Just about every article I’ve read concludes because there is no THC in that of CDB oil, it is safe to take and will not alter your mental state.
              Again, I’m not looking for the high at all, I’m strictly looking for something to help with the chronic pain I have day in/out.

  5. This is a solid scientific assessment of both the potential harms and benefits of cannabis use! It is very important that we understand the true nature of the drug before we decide to put it into our bodies. I really agree with your overall conclusion in the drug not being a healthier simply because it’s natural, and that research needs to continue on the subject. I think objective research and education will be much more powerful in deterring people from the drug. This is why this is a particularly great post; because it uses scientific research to support your claims. Hopefully we can continue to gain scientific evidence, but this is also a controversial subject at the moment. Great job summarizing the current state of cannabis research!

  6. If you have chronic pain cannabis is not a theoretical discussion

    You are faced with a few choices

    There are the internal devises
    A phentnyl lump or electrical stimulator

    Nerve killing surgeries



    Or throw the pills away and summon your own endorphins through aerobic exercise

    I went from 8 pills a day, phentinyl patch to none

    Cannabis, meditation and aerobic exercise

    You have to make a choice or suffer

  7. This field is expending in a tremendous way that nobody ever expected it to! I think we have to wait and see, what more research and studies will provide ! thanks for sharing !

  8. I have looked into CBD for a while. I haven’t tried it because there is no scientific evidence it will work. I was surprised when I heard pharmacies would be selling it

    1. It’s unfortunate that the process for getting herbal supplements andthat kind of thing into stores has a very low bar in terms of demonstrating effectiveness for any kind of health condition.

  9. I’ve found great benefits for my mental health using marijuana, reduces my mood swings & helps when I’m depressed. But I still need other meds with it. I think there needs to be more research. I know there’s conflicting studies on whether it damages adolescent brains or not. They use to tell us it kills brain cells, come to find out it doesn’t. I think it depends on each person. I’ve seen some people who get extra paranoid while it helps my anxiety. I’ve seen others use because they’re depressed and others who became depressed because they used. I do know it’s great for pain, though.

    1. Yeah the effects on mental health seem to vary quite a bit from one individual to the next, but the positive effect for pain seems a lot more consistent.

    1. I think it’s a good idea for anyone with a mental illness to be careful about what they’re putting in their body. You certainly don’t want to try something that might potentially worsen your illness!

  10. Some of those studies make me question whether the weed caused people to have suicidal ideation and depression or whether they were using cannabis as a way to deal with the emotional problems that were already present.

    For me, cannabis has been both helpful and harmful depending on how much I use. I agree that when it’s abused (used 2 or 3+ times per day) it’s caused me to become paranoid, anxious and lazy. However, if I’m just hitting the sweet spot of approximately 1 time at night before bed, it’s the perfect amount to just wind me down, relieve my stress and lull me to sleep. As long as I keep it in that sweet spot, I’m a firm believer that cannabis has helped to improve my life in massive ways! It’s also helped me stay away from alcohol which I was abusing before Cannabis, off and on. Certainly a healthier alternative.

    More research would be nice. Great post.

  11. Like a number of others here, I live with a serious “mental illness”, namely bipolar disorder, and find cannabis helpful.

    I find edible cannabis (of the sort that gets you high) hugely beneficial in managing myself. I have found that cannabis actually helps when I’m depressed, it lifts me up, brings a little joy and light into my life when I’m having dark times. Anecdotally it appears plenty of those with a mental health diagnosis use cannabis to ease their life. A friend living with anxiety eats cannabis edibles to help with her off days. I know people living with a schizophrenia diagnosis who find cannabis calms them. This is what the anti brigade won’t tell you – cannabis actually helps many people with “mental illness”. Eating cannabis has enabled me to train my mind to think positively, through ruminations while high. For this, I am grateful, and happier than at any time before in my life.

    There is not much research on using cannabis to help with mental illness, mainly because until the last few decades researchers COULD NOT legally investigate. I am hopeful that in coming decades there will be a lot more research. One 2018 study showed that of

    Finally, I recommend everyone who lives with a so-called “disorder” to find out about Mad Pride. We are not second class citizens.

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