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The perception divide: Prior cannabis use shapes perceived outcomes of its effects

  • Individuals with prior cannabis use tend to emphasise the benefits and downplay the potential harms of cannabinoids.
  • Without careful analysis of user perceptions, results may not reflect the true pharmacological effects of cannabis, impacting how they are used therapeutically or recreationally.
  • How can the effects of cannabis compounds be accurately assessed, taking into account user perceptions?
  • Professor Sean Barrett, Dalhousie University, Canada highlights the importance of targeting such beliefs to optimise the potential benefits and minimise potential risks of different cannabis compounds.

Cannabis (Cannabis sativa) use has long been a subject of scientific inquiry, with studies exploring both the benefits and harms associated with its use. Although it is widely acknowledged that the pharmacological effects of a substance can vary between individuals due to differences in genetic composition, it is important to recognise the significant psychological component involved in how a person reacts to a drug.

Dr Sean Barrett, Professor in the Department of Psychology and Neuroscience at Dalhousie University, Canada, has spent significant time exploring the psychological component of cannabis use. He asks the question: what factors contribute to the effects of cannabis? Is it the plant or the people’s perception of the plant? His research reveals fascinating conclusions, suggesting that it is likely a combination of both.

What is cannabis?

The cannabis plant contains over 100 cannabinoid compounds, chemical substances that can activate cannabis receptors in the body. Cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC) are used to treat various psychiatric and medical conditions. They can be inhaled or ingested for a more slow-release effect, and are two of the most widely studied cannabinoids. However, our understanding of the public’s beliefs regarding the effects of these compounds is limited.

“What factors contribute to the effects of cannabis? Is it the plant or the people’s perception of the plant?”

CBD is commonly used for therapeutic relief such as pain neutralisation, as an anti-inflammatory, an anti-cancer drug, as well as to treat seizures. It does not appear to result in the mind-altering effects that can be induced by THC. THC has not gained as much therapeutic traction, largely due to its power to alter sensory and time perception and its potential to cause psychosis. THC gives more of a mental high in addition to the effects on the body, with users reporting a state of calm or elation and enhanced creativity. People in extreme pain, for example post medical surgery, report significant benefits from THC use. The harm versus benefit remains an area of debate for both THC and CBD, even though CBD does not induce mind-altering effects to the extent that THC can.

One reason for this is that the factors influencing its effects are not limited to the chemical constituents of the plant, but largely depend on one’s opinion of it, according to Barrett, a world-leading expert on cannabis use. These opinions or beliefs tend to come from whether they are a regular user or non-user.

Individual differences in response

Chemicals infer reactions in the body and mind which can be both negative and positive. But to what extent are the effects down to an individual’s perception of what is going to happen? Having an expectancy of what a drug is going to do to you is almost like a filter. The same dosage of drug can be taken by two different individuals, but their beliefs or thoughts about it act as an important layer that influences the final outcome for them. Factors such as information presented to the user (eg, media, verbal communication), observation of others, and personal experience can shape and strengthen these expectations.

“‘…targeting such beliefs might be one way to maximise potential beneficial effects and minimise the potential harms of various cannabis compounds.’”

This is a crucial factor to consider when analysing the potential benefits or harm of CBD and THC. It is not going to be the same for everyone, but those without prior experience could be missing out on significant health benefits and misguiding the public perception to believe that the negative effects are worse than they are. On the contrary, ongoing users might overstate the benefits and reduce the negative outcomes. It is not that this is necessarily a negative, more that their preferences for the drug may not be replicated in others.

Figure 1. The effects of cannabinoids (THC, CBD, THC & CBD combined) in people with prior cannabis use (vs no prior use) rated all cannabinoids higher regarding their association with many therapeutic and positive effects, while endorsing weaker expectancies about their role in some negative effects. From Spinella TC, et al, (2003) Addictive Behaviors,

Cannabis effects: Users versus non-users

A recent study by Barrett and colleague Ms Spinella revealed that participants who strongly believed CBD can reduce anxiety reported a significant reduction in their anxiety symptoms, even when they received an inactive placebo – a remarkable bias. In a follow-up study, the researchers collected perceptions of the effects of CBD, THC, (taken separately or in combination) from adult users and non-users. Participants rated CBD-containing products higher for therapeutic effects such as relief from stress, anxiety, or pain, while THC-containing products were rated as being more potent for non-therapeutic effects such as creativity improvement, or risk of addiction and psychosis. Individuals with prior cannabis use rated both compounds higher for their therapeutic and positive effects, but had weaker beliefs about their potential negative effects such as addiction or psychosis.

As Barrett explains, ‘Because an individual’s beliefs about a substance can impact how it is used, as well as the effects experienced, targeting such beliefs might be one way to maximise potential beneficial effects and minimise the potential harms of various cannabis compounds, whether they are used recreationally or in a therapeutic context.’

With such a powerful plant the potential to do good and harm is significant when advocating for its use. Barrett’s research is vital in helping us understand the vastly different effects of cannabis compounds, which vary depending on previous usage or experience. It is not that these perceptions are ‘good’ or ‘bad’, but it is important to be aware of how powerful they are in altering how a drug can actually work in the body. If studies separately evaluate these expectancies, more realistic conclusions can be made about their potential benefits and harms.

Prior use seems to just account for a one-time use. Does taking cannabis just one time have such an influence on these results, compared to someone that has taken it numerous times?
Beliefs about the benefits and harms of a given substance tend to be fluid and informed both by previous first-hand experiences as well as the observations of others. Overall, more frequent users tend to have more accurate expectations and beliefs about the effects of a substance relative to novice users, but this isn’t always the case. For example, heavy users appear to be more likely to downplay potential harms. 

How do you suggest people change their beliefs around potential benefits or consequences: whether they are a user or non-user?
First, it is important for individuals to understand and acknowledge that their beliefs, attitudes, and expectations have the potential to interact with a drug’s pharmacological effects to produce the overall experienced effect. Thus, if you expect that a treatment will have no benefits, chances are that it won’t. However, it is also important to recognise that not all sources of information provide accurate information about a substance’s potential benefits and harms, and inaccurate information can itself be harmful. I would suggest that potential users seek out credible sources of information (eg, peer reviewed scientific articles) and that clinicians tailor the information about potential drug effects to the intended purpose of the users.

How can someone get over the hurdle of being a non-user to being a user if their results might already be jeopardised prior to them being a user?
Many non-users may be reluctant to try a substance due to inaccurate beliefs about its potential risks or harms, and such beliefs could be a self-fulfilling prophecy. Before trying a new drug, it is important for prospective users to seek out credible information about its potential harms and benefits as well as to understand their likelihood. Because many non-users have an exaggerated view of how risky or harmful a drug like cannabis is, it could prevent them from taking a substance that might have some benefits. On the other hand, many users tend to downplay the risks associated with cannabis use and this could lead to its continued use, even when it is causing harm.

Would you recommend cannabis compounds THC or CBD for first time users?
That would depend on a lot of factors, such as an individual’s purpose for using the drug as well their individual characteristics such as age, and medical history. For example, although CBD is generally safe, it has the potential to interact with various medications and it might not be suitable for some individuals. On the other hand, THC might be less likely to interact with some medications, but it can be risky for younger individuals as well as for those known to be at risk for mental illness or addiction. That said, if you are looking to alter your mood and perceptions, THC may be more desirable, but if want to avoid any intoxicating effects CBD could be more desirable.


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