One of the most common claims about cannabis is that it relieves stress and helps one to relax. A new study demonstrates that this may well be true, but only at lower doses. The results are published in Drug and Alcohol Dependence.

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Research shines light on the ability of cannabis to reduce stress.

Laws on marijuana use for medicinal purposes have changed dramatically over recent years. However, because the drug is a highly regulated category 1 substance, it is difficult to obtain permits to study it.

A group of researchers from the University of Illinois at Chicago (UIC) and the University of Chicago, IL, leaped through the appropriate legislative loops to investigate the effects of tetrahydrocannabinol (THC) – which is the main active ingredient in cannabis – on stress.

They wanted to test the age-old adage that cannabis helps people to relax and can relieve stress. Although many people have heard these claims, there has been little scientific study on the matter.

As Emma Childs, associate professor of psychiatry at the UIC College of Medicine, says, “Very few published studies have looked into the effects of THC on stress, or at the effects of different levels of THC on stress.”

The team from Chicago set out to investigate cannabis’ stress-relieving properties at different doses. In all, 42 healthy volunteers aged between 18 and 40 were studied. All had some experience of cannabis but were not daily users. They were split into three groups:

  • the low-dose group, who received a capsule containing 7.5 milligrams of THC
  • the moderate-dose group, who received a capsule containing 12.5 milligrams of THC
  • the placebo group, who received a capsule containing no THC

Although it is difficult to equate ingested cannabis to smoked cannabis, Prof. Childs says, “The doses used in the study produce effects that are equivalent to only a few puffs of a cannabis cigarette.” She goes on to explain the dose choices, saying, “We didn’t want to include a much larger dose because we wanted to avoid potential adverse effects or cardiovascular effects that can result from higher doses of THC.”

Neither the participants nor the investigators knew what doses had been given to which individuals.

Each participant took part in two 4-hour sessions, which were 5 days apart. They took the capsule, then relaxed for 2 hours, allowing it to enter the bloodstream.

In the first session, the participants had to spend 10 minutes getting ready for a mock job interview. They then had a 5-minute interview with laboratory assistants, who did not offer positive verbal or body language feedback. Next, they were asked to carry out a challenging mathematical task for 5 minutes – a task that, according to Prof. Childs, is “very reliably stress-inducing.”

During the participants’ second visit to the laboratory, they were asked to talk about their favorite movie or book for 5 minutes, and then to play solitaire for a further 5 minutes.

At the start, during, and after both sets of tasks, participants were asked to rate their stress levels and feelings about the task. Also, throughout the tests, heart rate, blood pressure, and levels of cortisol (a key stress hormone) were measured.

As predicted, those who received the low dose of THC reported less stress after the psychosocial test than those given a placebo. Also, their stress levels dropped faster after the test.

However, those receiving the higher dose of THC reported a more negative mood before and during the task. Beforehand, they were more likely to rate the psychosocial task as “challenging” or “threatening.”

Also, the moderate-dose group paused more during the mock interview than the placebo group did.

Across all three groups, there were no significant differences measured in blood pressure, cortisol levels, or heart rate before the task, during it, or afterward.

Our findings provide some support for the common claim that cannabis is used to reduce stress and relieve tension and anxiety.

At the same time, our finding that participants in the higher THC group reported small but significant increases in anxiety and negative mood throughout the test supports the idea that THC can also produce the opposite effect.”

Prof. Emma Childs

Although the study is on a relatively small scale, the findings are important because they begin to plug some gaps in our knowledge. Because of regulatory obstacles, investigating cannabis’ effects is difficult. But, at the same time, medicinal cannabis use is rising, making research more vital than ever.

With this kind of study, we are always left with more questions than answers. Would the results have been the same if the study had recruited people who smoked cannabis regularly, or people who had never tried cannabis? How would a higher dosage of THC have affected the results? Does inhaling rather than ingesting it make a significant difference? It would also be interesting to know whether the same effect would be seen in other types of stressful task, such as driving a car.

As ever, more research will increase our understanding, as well as either confirm or reject these findings.

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