Cannabis relieves stress in female rats – study

A new study has found that long-term cannabis consumption reduced response to stress in female rats.

The research also indicates that there could be significant differences in how chronic cannabis consumption affects men and women.

Female rats that inhaled vaporised cannabis daily for a month developed a blunted physiological response to stress, according to a new study by Washington State University researchers.

In contrast, male rats that had access to the same potency of cannabis over the same 30-day window, did not experience any physiological changes in how they responded to a stressful situation.

The WSU scientists’ work, published in the journal Neurobiology of Stress, also establishes a direct relationship between chronic cannabis consumption and dampened stress reactivity.

“We were able to show pretty conclusively that chronic cannabis use can, in fact, significantly dampen stress reactivity in female rats,” said Carrie Cuttler, an assistant professor of psychology at WSU and co-author of the study.

“Until now, no one has been able to establish whether this blunted stress response is the cause or the consequence of cannabis use.”

Researchers haven’t yet been able to link smoking cannabis to a muted stress response as in human studies, as they can’t practically or ethically randomly assign their test subjects to use cannabis or prevent them from consuming the drug for a period of time before beginning an experiment.

Those interested in examining the chronic effects of cannabis have tended to rely on animal models, where rats are injected with isolated components of cannabis to study the effects of the drug.

Ryan McLaughlin, an assistant professor of integrative physiology and neuroscience at WSU and a co-author on the paper, commented: “The problem with this approach is that it’s stressful to the rats and doesn’t recruit the same neurobiological circuits that taking a drug of your own volition does.

“To address this challenge, we developed a more natural cannabis delivery system that enables rats to self-administer vaporised cannabis whenever they feel like it.”

McLaughlin and his team trained rats to poke their noses into a hole with an infrared beam inside whenever they wanted a puff of cannabis vapor.

Researchers then measured levels of the stress hormone corticosterone before and after a 30-day period in male and female rats. These were put into either a control group that was not given cannabis or one of three experimental test groups that were given access to cannabis of low, medium, or high potencies.

Initially, all of the rats had similar spikes in corticosterone levels when confronted with a stressful situation. After the 30-day self-administration period, only the female rats that had access to the medium potency cannabis demonstrated a significantly muted physiological response.

The rats that were given access to the medium potency cannabis also tended to respond more to the substance and had higher concentrations of the drug in their blood after the experiment.

“Interestingly, we found that the rats that were given access to higher potency cannabis tended to respond less and had lower concentrations of THC in their blood after the experiment than the rats that had access to the medium potency cannabis,” McLaughlin said.

“What is causing this difference as well as why females seem to be more receptive to the stress muting effects of cannabis are both things we plan to investigate in the future.”

While McLaughlin and Cuttler’s work suggests cannabis might have some benefits in improving resilience to stress, the two researchers emphasised that the release of stress hormones typically serves an adaptive purpose, allowing an individual to mobilise energy stores and respond appropriately to threats in the environment.

Cuttler added: “An inability to mount a proper hormonal response to stress could have detrimental effects that could potentially be harmful to the individual.

“Research on cannabis is really just now ramping up because of legalisation, and our work going forward will play an important role in better understanding both the benefits and potential consequences of chronic cannabis use in women and men.”