There is an episode of BBC Horizon with the title Cannabis: Miracle Medicine or Dangerous Drug?, presented by Dr Javid Abdelmoneim.

During the documentary Abdelmoneim meets Dr Amir Englund, a scientist who is conducting a research to developer safer types of recreational cannabis. He is then the subject of an experiment testing in separate dates four different compositions of THC and CBD. The experiment involves the study of the thoughts and the feelings of the subject during the high and the investigation of any sign of psychotic behaviour through some psychiatric tests.

During the first test the presenter (at about 29 mins) says

I am beginning to think this is a trick on my patience

Then the scientist says that the presenter is becoming a bit suspicious. Then the presenter says

You are tricking me

This was judged by the scientist as a an event of paranoid behaviour.

During the second test the presenter (at about 34 mins) says

this times I am a lot more mellow

During the final review (at about 54-56 mins) this test was judged positively for the absence of paranoid behaviour.

During the final review it was also explained that the cannabis used for the first test had no CBD, only THC, while the cannabis used for the second had three times as much CBD as THC.

At the end of the documentary (57m45), Abdelmoneim claims:

Amir's study suggests that it is possible to make recreational cannabis safer.

Can the results of that experiment give a clue on how to address the risks of psychosis? I understood that the risk of psychosis was related to the long term use of cannabis and I also thought that it was caused by the fact that the long term use reduced the inner capacity of activating the neuro-receptors, thus increasing anxiety and similar conditions when the person is not under the effect of cannabis.

If so, the thoughts developed during a high have nothing to do with it. Serious research aimed at reducing the risks of recreational cannabis should test the long term effect on the neuro-receptors, not the effects of one or few highs on some individuals who are not regular users.

What I would like to know is if the documentary misrepresenting how cannabis might cause psychosis and how it could be prevented. This could be broken down in two questions:

  • Could adjusting THC and CBD ratios in recreational cannabis lower the risk of psychosis?
  • Can an experiment done on a number of casual users, that mainly studies the subjects behaviour during the high, be used as an evidence for the possible effects on long term users when they are not on a high?

This question is focused on the second point.

  • 2
    Of course the question has merit and I don't want to talk it down, but on a meta level I find it rather funny: "If we change the concentrations of active ingredients in a drug, do the side effects change?"
    – kutschkem
    Feb 27 at 8:08
  • Link to full study by Dr. Amir Englund (ResearchGate). Feb 27 at 22:55
  • @JiminyCricket. I see that the abstract states that the study produced no evidence. It means that in a documentary seen by million of people they let them think something then in a paper that few thousands people will read they say the opposite. Not nice, but in any case it does not matter, because the question is about the validity of the methods employed in the study, not about the study results.
    – mustermax
    Feb 27 at 23:13
  • @mustermax: That is not a fair summary. The documentary was shown in 2019, and showed Englund conducting experiments. The quoted paper was released 3 months ago, presumably with some results of those experiments. The main claim about CBD ratios affecting long-term psychosis came from Dr Marta Di Forti, not Englund, whose claims I quoted and you edited out for unclear reasons.
    – Oddthinking
    Feb 28 at 1:57


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