Introduction

Anxiety is one of the most common mental health disorders, affecting approximately 4% of the global population. Although there are many treatment options, such as talking therapies and medication, anxiety tends to be challenging to treat and relies heavily on the individual. In addition, long waiting times and side effects may deter people from seeking treatment. Hence, many individuals may seek out alternative approaches. One such alternative approach is using cannabis, which some research suggests can help some individuals manage anxiety. However, it is unclear whether improvements in an individual’s anxiety are due to the effects of cannabis or due to the placebo effect. Below, we will take a closer look at the research linking cannabis and anxiety, whilst also considering the placebo effect. 

The placebo effect

Interest in cannabis as a medical treatment is on the rise.¹ Some studies show that cannabis users report an improvement in depressive symptoms and improved mental well-being.^2,3 However, whether cannabis relieves anxiety or not remains controversial, with just as many studies showing the contrary. One possible explanation for these discrepancies is the placebo effect. 

The placebo effect is considered a false improvement in condition, due to preconceived mental biases about the treatment. Studies of anxiety are specifically prone to the placebo effect because anxiety is a highly subjective experience and is influenced by personal expectations. Furthermore, since anxiety affects both the mind and body, even a small change in mindset or physical symptoms can lead one to believe a treatment is working, even if it isn’t. The impact of the placebo effect is significant in fields like pain, anxiety, Parkinson’s disease and even some surgeries.⁴  

Several factors influence the strength of the placebo effect when examining cannabis and anxiety. These include previous exposure to cannabis and positive media reviews. In one study conducted by researcher Vanda Faria and team, it was shown just how much a person’s expectations about a treatment can influence the results.⁵ The researchers tested a commonly prescribed antidepressant, escitalopram, which is effective in the treatment of anxiety. Some of the participants were told about the drug they were taking, and the others were informed that they were on an ‘active placebo’ - a substance that doesn't actually treat anxiety, but mimics some of the effects of the real drug. According to self-reported ratings, the effect of the drug in the group who knew about their treatment was double that of the group who thought they were taking the placebo. Even more interestingly, the brain appeared to respond differently in these two situations. This study highlights how greatly the placebo effect can influence research results.

Cannabis and anxiety

The two main active substances in cannabis are tetrahydrocannabinol (THC) and cannabidiol (CBD). These chemicals are called cannabinoids. Whilst both THC and CBD affect the brain, THC is considered the main “psychoactive” cannabinoid, whereas CBD is considered the main “non-psychoactive” chemical component of cannabis.⁶ Depending on the doses, both of these chemicals have the potential to relieve anxiety. 

What makes cannabis an interesting choice for the treatment of anxiety is that anxiety is also a relatively common side effect of cannabis use. The risk of anxiety increases when someone is not a regular user or if the dose of cannabinoids is too high.⁵ This complex relationship between cannabis and anxiety further complicates scientific studies looking to investigate whether cannabis is an effective treatment for anxiety. Despite this, anxiety remains one of the most frequently cannabis-treated conditions.⁷ 

Psychological and social factors

The reason why anxiety is difficult to study is that research on this condition often depends on participants’ self-reports.. As a result, many factors can influence the size of the placebo effect and, consequently, the outcomes of the study. These factors include: ^8,9

• Personality traits such as optimism 
• Cultural and social influences
• Illness-related factors, i.e. duration and severity
• Social desirability bias (the tendency to answer questionnaires in a way that seems most socially acceptable)
• General challenges associated with self-reporting

Cannabis and the placebo effect

Research into the effectiveness of cannabis for relieving anxiety has produced mixed results. In many studies where cannabis is compared to a placebo, and participants are not informed of which treatment they are receiving, cannabis does not appear to have a significant effect on anxiety.¹⁰ This raises the question of whether cannabis is genuinely effective in managing anxiety or whether the improvement in symptoms is due to participants’ expectations. 

Expectations versus reality

Expectations can influence the improvement of anxiety symptoms. It has been found that patients who believe in the anxiety-relieving properties of cannabis tend to report lower levels of anxiety after using the drug.¹¹ This means that even just the belief that cannabis will help is enough to significantly improve symptoms. 

The strength of this expectation effect can vary depending on several factors. These include things like exposure to positive media coverage and previous positive experience with cannabis.¹² 

Implications for treatment and research

Challenges for researchers

The placebo effect makes it difficult to separate the real effects of medications from those driven by expectations. This presents a challenge in developing new therapies for mental illnesses like anxiety. Researchers must be careful in designing their studies to minimise the impact of the placebo effect on results. This would help in providing a clearer picture of the actual effects of cannabis on anxiety. 

Potential benefits of the placebo effect

Although the placebo effect is often seen as a challenge by researchers, it can actually benefit people seeking relief from anxiety. The placebo effect might also encourage those living with anxiety to make positive life changes or act as a support while waiting for other treatments, like talking therapies. 

Summary

Cannabis has been shown in research to help with symptoms of anxiety. However, the relationship between cannabis and anxiety is a complex one and is heavily influenced by the placebo effect. The placebo effect refers to a false improvement of anxiety symptoms that is not due to the treatment itself, but rather the belief that the treatment will work. This effect plays a significant role in anxiety research, which is one reason why new treatments for this disorder are relatively rare.

The impact of cannabis on anxiety is highly controversial within the scientific field, with evidence showing that it can both improve and worsen symptoms. Studies have shown that even just the belief that cannabis can help with anxiety can lead to an improvement in symptoms, regardless of whether participants take cannabis or a  ‘dummy’ drug. 

Several factors influence the strength of the placebo effect when examining cannabis and anxiety. These include previous exposure to cannabis and positive media reviews. In the context of anxiety, the placebo effect is shaped by personality traits such as optimism, social factors like cultural acceptance and illness-related factors, such as how long the person has had anxiety and how severe it is. 

FAQs

Can anxiety cause placebo effects?

Yes, people diagnosed with anxiety are prone to a higher placebo response. This is because anxiety is highly subjective, and treatment efficacy is influenced by expectations. 

Can the placebo effect cure mental health issues?

No. The placebo effect is a temporary phenomenon that may help to relieve symptoms, but it does not address the root cause of mental health conditions. Placebos cannot replace traditional treatments such as talking therapies. 

Is cannabis safe for anxiety?

Whilst there is some evidence for cannabis having a beneficial effect in some individuals experiencing anxiety, experts warn that using cannabis when diagnosed with a mental health condition can worsen symptoms or lead to risk-taking behaviours. 

How long does the placebo effect last?

The placebo effect will not cure you. However, in mental health-related conditions, the positive effects of a placebo can last for up to a year.  

How do you overcome the placebo effect?

To minimise the placebo effect in studies, researchers require a good study design. In clinical trials, some researchers train participants on how to complete questionnaires in ways that reduce external influences which could shape their expectations and affect the results.¹³