A new study conducted by researchers at the University of York finds men are more likely to suffer from cannabis psychosis than women. To date, there have been many studies examining the link between cannabis — the most used illegal substance in the United Kingdom — and psychosis, but this is the first to study the ways in which it affects men and women differently.

So what exactly is cannabis psychosis? Most people describe it as a delusion, hallucination, or feeling of paranoia that sometimes occurs after using marijuana, although some believe marijuana is capable of much more, such as inducing mental illnesses linked to psychosis, like schizophrenia, and exacerbating preexisting psychosis.

According to NPR, nine studies have been conducted on the link between marijuana use and the development of schizophrenia, all but one finding evidence in the affirmative. NPR went on to cite the National Institutes of Health, who suggests the link between the two does not prove causality, but rather displays that those with preexisting psychosis are more likely to smoke marijuana.

York’s Department of Health Sciences decided to take it a step further and see if cannabis psychosis was more prevalent in men or women, if at all. Using data collected over an 11-year period, researchers observed the differences between men and women using cannabis, as well as their respective progression to cannabis psychosis. The results were published in the Journal of Advances in Dual Diagnosis.

Researchers discovered that statistically, there are twice as many men using cannabis than women. Previous rates of cannabis-induced psychosis mirrored this dichotomy; men outnumber women incidences of cannabis psychosis by 2:1. However, researchers are noticing this gap is widening. Researchers suggest the ratio of men to women experiencing cannabis psychosis is now closer to 4:1.

“The marked gender difference in rates of cannabis psychosis is puzzling,” said Ian Hamilton, study author and lecturer in mental health at York, in a recent press release. “It is possible that mental health and specialist drug treatment services, which have a disproportionate number of men, are identifying and treating more males with combined mental health and cannabis problems. However, it is also possible that women with cannabis psychosis are not being identified and offered treatment for the problems they develop.”

Previous research has also found that cannabis users are more likely to experience psychosis if the strain of marijuana is more potent. For example, King’s College London conducted a study in February and found a strain of weed often referred to as “skunk” induced 410 hospital visits for first-time users.

Even so, researchers still can’t say for sure why men and women experience cannabis psychosis differently. They hope to continue their research in the future in an effort to examine whether women are, in fact, seeking treatment less for instances of cannabis psychosis than men.

For now, Hamilton claims to know one thing for sure.

“When it comes to cannabis psychosis, gender does matter.”

Source: Hamilton I, Galdas P, Essex H, et al. Cannabis psychosis, gender matters. Journal of Advances in Dual Diagnosis. 2015.

Di Forti M, Marconi A, Carra E, et al. Proportion of patients in south London with first-episode psychosis attributable to use of high potency cannabis: a case-control study. The Lancet Psychiatry. 2015.