Bisexual women had higher rates of past-year and daily marijuana use compared to heterosexual women, according to a study just published at Columbia University Mailman School of Public Health. Gay/lesbian women were also more likely to report daily marijuana use and past year medical marijuana use than heterosexual women. While previous research has explored the association between state-level medical marijuana laws (MMLs) and marijuana use (MU) and MU disorder (MUD) among the general U.S. population, this is the first to explore this relationship for lesbian, gay and bisexual (LGB) individuals, including gender differences. The findings are online in the journal Drug and Alcohol Dependence.

"Our work builds on the Institute of Medicine report highlighting the importance of conducting additional research on LGB populations across the life course," said Morgan Philbin, PhD, assistant professor of Sociomedical Sciences at Columbia's Mailman School. ""While research has explored how LGB discrimination polices may impact substance use, less work has explored how substance use policies may impact LGB men and women differently than heterosexuals."

The researchers analyzed data from 126,463 adults 18 and older in the 2015-2017 National Survey on Drug Use and Health to study the odds of past-year marijuana use, any past-year medical marijuana use, daily/near-daily marijuana use, and marijuana use disorder. They also tested the interaction between residence in a state with medical marijuana laws and sexual identity.

When the researchers examined the relationship between state MML status and MU outcomes they found that gay/lesbian women in MML states had higher daily/near-daily (300+ days/year) MU than gay/lesbian women in non-MML states while bisexual women in MML states had higher past-year use than bisexual women in non-MML states; both lesbian/gay and bisexual women in MML states had higher medical MU than those in non-MML states.

"We further extended these findings to estimate daily/near-daily MU prevalence, which was seven times higher among bisexual women than heterosexual women and 2.3 times as high for bisexual men compared to heterosexual men," noted Silvia Martins, MD, PhD, associate professor of Epidemiology and senior author.

Past-year marijuana use was 10 percent among heterosexual women, 26 percent among gay/lesbian women and 40 percent among bisexual women. Daily use was lower among heterosexual women (1.5 percent) compared to lesbians (6 percent) and bisexual women (10 percent). Similar patterns emerged for past-year marijuana use disorder.

Past-year marijuana use for medical reasons was reported by slightly more than one percent of heterosexual women, 5 percent of lesbian/gay women and 5.5 percent of bisexual women.

Compared to heterosexual men (17 percent), past-year use marijuana was higher among bisexual men, (30 percent) and gay men (29 percent). Daily marijuana use among men was highest among bisexual men (9 percent) followed by gay (7 percent) and heterosexual men (4 percent). Any past-year medical marijuana use was 2 percent among heterosexual men, 5 percent among gay men and 4 percent among bisexual men.

Rates of daily marijuana use or marijuana use disorder for gay men did not differ significantly in states that had passed medical marijuana laws compared to states that had not passed these laws.

While beyond the scope of these analysis, the difference in policy effects of medical marijuana laws for bisexual women compared to heterosexual women may be a result of the high levels of stigma faced by bisexual women, according to the researchers. This could result in self-medication with medical marijuana even in states without MMLs if LGB adults are in part using marijuana to alleviate sexual minority stress.

"Our results support existing literature by demonstrating that bisexual women have higher marijuana use disorder compared to heterosexual women. This is part of a larger health burden, as bisexual women are twice as likely to have co-occurring mental health and substance use disorders yet often have little contact with service providers," observed Philbin.

"This study represents an important contribution to the literature on the structural determinants of substance use for LGB individuals and demonstrates the need to allocate resources that target sexual minority women, especially as medical marijuana laws and recreational marijuana laws continue to change at the state level," said Martins. "Future surveys that capture how individuals identify will help us pinpoint how state-level marijuana policies may differentially impact specific sub-populations, ultimately advancing the development of more health-promoting policies for all."