How cannabis makes thoughts tumble

Cannabis smokers often report that when stoned, their thoughts have a free-wheeling quality and concepts seem connected in unusual and playful ways. A study just published online in Psychiatry Research suggests that this effect may be due to the drug causing ‘fast and loose’ patterns of spreading activity in memory, something known as ‘hyper-priming’.

Priming is a well studied effect in psychology where encountering one concept makes related concepts more easily accessible. For example, classic experiments show that if you see the word ‘bird’ you will react more quickly to words like ‘wing’ and ‘fly’ than words like ‘apple’ and ‘can’ because the former words are more closely related in meaning than the latter.

In fact, it has been shown that the more closely related the word, the quicker we react to it, demonstrating a kind of ‘mental distance’ between concepts. Think of it like dropping a stone into a pool of mental concepts. The ripples cause activity that reduces in strength as it moves away from the central idea.

‘Hyper-priming’ is an effect where priming happens for concepts at a much greater distance than normal. For example, the word ‘bird’ might speed up reaction times to the the word ‘aeroplane’. To return to our analogy, the ripples are much stronger and spread further than normal.

The effect has been reported, albeit inconsistently, in people with schizophrenia and some have suggested it might explain why affected people can sometimes make false or unlikely connections or have disjointed thoughts.

As cannabis has been linked to a slight increased risk for psychosis, and certainly causes smokers to have freewheeling thoughts, the researchers decided to test whether stoned participants would show the ‘hyper-priming’ effect.

The experiment used a classic ‘lexical decision task‘ where the volunteers are shown an initial word (‘time’) and then after a short gap are shown a nonsense word (‘yipt’) and a true word (‘date’) at the same time and have to indicate as quickly as possible which is the real world.

The experimenters altered how related the initial word and true word were to test for the semantic distance effect, and also varied the gap between the initial word and the test to see how long the priming effect might last.

Volunteers who were under the influence of cannabis showed a definite ‘hyper-priming’ tendency where distant concepts were reacted to more quickly. Interestingly, they also showed some of this tendency when straight and sober .

Cannabis also had the effect of causing temporary psychosis-like distortions as would be expected from a psychedelic drug, but the smokers did not make more errors and were not more likely to report psychosis-like symptoms when sober, suggesting the effect was not due to general mental impairment and couldn’t be explained by underlying tendency to mental distortion.

Although the debate is not completely settled, there is now good evidence that cannabis causes a small increased risk for developing schizophrenia particularly when smokers start young. In fact, additional evidence on this front was published only this week.

The researchers discuss the possibility that long-term smokers who spend a lot of time in a chronic ‘hyper-primed’ state might make psychosis more likely by loosening the boundaries of well-grounded thought, although exactly how cannabis raises the risk of psychosis, and indeed, how exactly it affects the brain, is still not understood well-enough to make a firm judgement.

Link to PubMed entry for cannabis ‘hyper-priming’ study.

9 Comments

  1. Posted March 10, 2010 at 6:24 pm | Permalink

    Thanks for the primer on hyper-priming. Fascinating.
    Although I am still not convinced about cannabis raising the risk for psychosis, especially schizophrenia. I think we’ve got the cart before the horse on this one: people who are genetically susceptible to schizophrenia often have their first significant psychotic break while on a psychoactive drug like LSD or cannabis. I don’t think we have good evidence that cannabis itself causes the psychoses. What we have is evidence that if you are genetically predisposed to schizophrenia, cannabis is one of many triggers, some social, some biological, that can contribute to the initial expression of a pre-existing condition.

  2. Axton
    Posted March 11, 2010 at 10:28 pm | Permalink

    I’ve been conducting similar “hyper-priming” experiments myself.

  3. will
    Posted March 14, 2010 at 12:08 am | Permalink

    I’m copying and pasting the same response I gave at Jonah Lehrers blog. Dirkh, this a story you might think upon a bit, its only anecdotal and is also first person (so it wont pass too many objectivity tests) but it might be useful to entertain.
    At age 18, I was diagnosed with schiotypal personality. It was more than a personality disorder, it seems now, as hallucinations and frank psychotic episodes were there, though the episodes were short lived. Delusions were also a constant. There was also a serious emotional disturbance, the depressive sort, something I’m told and I’ve read is usually not evident in schizophrenia. My diagnoses was changed to schizoaffective disorder.
    Around age 20, I began smoking pot. This did two things. One is, perhaps the semantic hyper-priming. I would be talking to friends I world free associate for hours at a time. I thought I was a virtuoso of improvisational thought, a young Zizek in the lonely midwest. I thought and spoke improvisationally when sober, in part because I was a serious reader and at that age (and still at 26) I was trying out idea after idea. However, this improvisation in thought and speech grew extremely exaggerated when I smoked marijuana.
    Here’s the great mystery. Marijuana had, in some sense, an antipsychotic function. I was in a relationship until age 20. I’d been in that relationship since age 16. A tragic problem in the relationship was my inability to have sex. When we would have sex I would have auditory hallucinations that were incredibly threatening. Since I enjoyed getting high, as did she, we began having sex high, as many people do. There were no voices when during intercourse if I was high. I became thoroughly involved with the sex and not only did the threats cease, but the past threats during sober intercourse didn’t bother me.
    I’m not recommending marijuana for the mentally ill
    In fact, because marijuana had the strange effect of partially resolving auditory hallucinations, I decided it would be wise to smoke it several days a week. This was a poor decision, though it did not make me more psychotic, it did reinforce my delusions and expand their scope. Probably through this semantic hyper-priming effect.
    Sometimes I think how terribly sad it is that researchers can’t (or wont) open up my head and watch what happens on their screens. It might be interesting. It might even be valuable. It might even entertain me for a while.

    • Lisa
      Posted October 30, 2011 at 2:55 pm | Permalink

      Will I need to talk to you plz email me

  4. Valerie Lambert
    Posted February 23, 2011 at 7:45 pm | Permalink

    Thanks! This is a great abstract.

  5. Anxy Chetr
    Posted November 13, 2012 at 12:53 am | Permalink

    sometimes after having a pot it seems i am going heaven teasing everything without a thought but the next to me always find the negative intension
    ]and that seems little distarius to me and after that i go on thinking to the same matter forgoting my wood and that is what i am still going with pot until i find why is this…so it could be the good decision..m confused but inner feeling always ask me to do..

  6. Paul
    Posted November 10, 2013 at 2:52 pm | Permalink

    This was a fascinating read. It may have just been my imagination, but I actually felt I could sense the differences in time it took me to read each word in the hyper-priming example. I had to definitely read ‘apple’ and ‘can’ but ‘wing’ and ‘fly’ jumped off the page. Reading ‘aeroplane’ felt similar to reading the filler words around the examples. Imagination or not I, as someone who has probably pumped multiple pounds of cannabis through my system, found the concept of cannabinoids aiding this thought process to play true, comparing my currently sober mind to that of before I was even remotely interested in drugs. Though maybe that’s purely because I was either too keen on what I was reading, am older now than when I first used or perhaps because I’m heavily sleep deprived and exhausted. Fundamentally the conscious is an awesome thing, and I’m glad mine just stumbled upon this site :)

    As to weed causing or helping to cause psychosis/skitzophrenia, I think, based on copious experience and observation, that I strongly side with Dirkh on the issue. I believe weed reduces REM sleep, increases general apathy enabling one to endure things they despise (predominantly limiting the drive to change situation) plus has an effect on memory whilst intoxicated (mainly concerning connections with activity and time) thus that when used frequently (especially with constant use) you can easily show symptoms of functioning at much lower levels, of which the user is greatly unaware of or very aware but apathetic towards. In some people this may place them on some kind of psychosis spectrum, but ultimately in a standard healthy person has little to no ill effect after discontinuation of use. Furthermore I think most people, *if they feel like it*, can genuinely improve themselves through the use of brain stimulation with psychoactive drugs.

  7. Paul
    Posted November 10, 2013 at 3:07 pm | Permalink

    I should add that constant or very frequent use of any substance is probably not the best choice. Everything in moderation they say. Though I feel slightly satisfied with my three years of solid stonering, I’d be lying if I told anyone that it was only positive. But it was barely negative save for the time spent wasting away. You can’t get that back, so to whomever decides to happen upon this writing – use yours wisely :)

  8. Jason
    Posted February 23, 2014 at 1:16 pm | Permalink

    Does this sound right? Like a machine, our brains generally operate at a steady capacity. “Normally,” the brain is in the mode of processing the 5 senses throughout the day and storing these experiences into either short-term or long term memory. When the brain is operating at capacity while processing the 5 senses into memory, it is again, operating at capacity which takes away from the brains capacity to hyper-prime or think freely.
    For those of us that are lucky enough, cannabis switches the brain’s mode of operation and cranks up production! In my opinion, this “free-thinking” is not what “they” want and is another reason that cannabis has been discredited and made illegal.


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