Cannabis, a Painkiller that is More Effective in Men than in Women

Today, numerous scientific studies and experiences have proven the effectiveness of cannabis to treat various health problems. Among these, pain is one of the most common: while some women use cannabis to relieve discomfort caused by menstruation, others take it as a remedy for a disease that accompanies them for life. According to Mark Ware, a researcher at McGill University in Montreal (Canada), "between 10 and 15% of chronic pain patients use cannabis as part of their pain management strategy."

In one of his latest studies, published in the 'Canadian Medical Association Journal' a few years ago, Ware precisely verified the effectiveness of the use of marijuana as a palliative for these medical conditions. His team conducted a clinical trial with adults suffering post-traumatic neurological and postoperative pain. After inhaling 25 milligrams of cannabis with a 9.5% THC content, three times a day for only five days, 12 women and 11 men who participated in the research felt less pain and slept better. Although his work included individuals of different gender, Ware made no distinction about the results.

However, "pre-clinical evidence suggests that the relief provided by cannabis products varies among the sexes," said Ziva Cooper today, neurobiologist of the Department of Psychiatry at Columbia University in New York. So far "no studies had shown this to be true in humans," says the expert. Most analysis took into account people of only one sex or did not consider sex to be an important factor in the investigation.

Now the results of a recent study by Cooper and his colleague Margaret Haney suggest that the analgesic power of marijuana is more effective in men than in women. This is the first research confirming this gender difference in the painkilling effect of the plant.

THC, the psychoactive compound of the plant, is one of those responsible for the medicinal use of cannabis, acting on the human endocannabinoid system. The body naturally produces very similar molecules that function as neurotransmitters or chemical messengers to regulate the response to different stimuli such as appetite and pain. The THC in marijuana simulates their behaviour and binds to the same receptors located in different parts of the body, but which are especially abundant in the brain. Its link to these centres causes a response in the nervous system which inhibits, in a varying degree, the sensation of pain.

To analyse this calming effect, the researchers did two tests with 49 smokers of both sexes –21 women and 28 men in total–who consumed marijuana for pleasure; i.e., they did not show any medical condition that caused them pain.

In the first stage of the study, volunteers smoked the same amount of marijuana or placebo substance, administered only to some of them to compare results. The second step was to introduce one of their hands in ice water and keep it submerged until they could no longer tolerate the pain. Finally, the authors asked participants to complete a questionnaire to assess both the degree of suffering they had experienced as well as the limit they had reached.

Thus, men who had consumed cannabis said they had felt less pain and developed a greater tolerance to it; i.e., its painful sensation decreased considerably and they could endure longer having their hand in cold water. However, women did not express any decrease in sensitivity. Although they admitted having experienced a slight increase in the threshold of pain immediately after smoking cannabis, the effect disappeared with time.

The authors suggest that this modest female response may be indicative of hyperalgesia or abnormal sensitivity to pain caused by opioids, a phenomenon associated with a prolonged use of these substances, which paradoxically increases susceptibility to pain. "It could mean that women are more susceptible to potential hyperalgesic effects of cannabinoids" they note in the study.

Despite these differences in the effectiveness of the analgesic potency of cannabis in men and women, the researchers found no variation between the sexes regarding the appearance of other psychoactive effects or the level of enjoyment obtained from consumption. 

More thorough investigations

Cooper and Haney point out that more studies are needed to identify the factors that influence the analgesic effect of cannabinoids in marijuana. Among them, the potency of the product, the way it is consumed (inhaled or oral), the frequency of use and the type of pain to be treated.

"This work highlights the importance of including both men and women in clinical trials to understand the therapeutic effects and the negative consequences of cannabis," says Cooper. And not only that: the neurobiologist and her colleague also recommend further analysis of the data obtained in investigations in search of possible variations between the sexes.

Performing more in-depth studies becomes relevant "especially because of the increasing number of people using products derived from the plant for medicinal or recreational purposes," says Cooper. She continues: "Although legalization of medical cannabis is spreading rapidly, its possible adverse effects still limit the process."

There are already cannabis-based analgesics which base their action on the active ingredients of the plant, like the painkiller Sativex, based on natural extracts of marijuana and administered as an oral spray. However, some ensure that the composition of this type of drugs, different from that of the plant does not produce the same effect as raw cannabis because it lacks the so-called "entourage effect" according to which all cannabis elements act better together than individually.

"It is imperative that both its medicinal properties and its possible harmful effects are studied under controlled conditions and comparing the results with a placebo, taking into account not only sex, but also the dose and the severity of each medical condition" concludes the expert of Columbia University. As evidenced, gathering as much information on the mechanisms of action of marijuana is key to contribute to the normalization of its therapeutic use.