The view among some scientists and doctors that frequent marijuana use may impair sexual performance has been challenged by new research from Stanford University which suggests that in fact, the opposite may be more likely.

"Frequent marijuana use doesn't seem to impair sexual motivation or performance," said Michael Eisenberg, senior author of the study. "If anything, it's associated with increased coital frequency."

While it is important to note that the research does not establish a causal connection between marijuana use and sexual activity, lead author Andrew Sun said the results hint that one may exist.

"The overall trend we saw applied to people of both sexes and all races, ages, education levels, income groups and religions, every health status, whether they were married or single and whether or not they had kids."

The study is the first to examine the relationship between frequency of sexual intercourse and marijuana use at the population level in the US. The results, which were based on an analysis of more than 50,000 American men and women aged 24-45, are published in the Journal of Sexual Medicine.

"Marijuana use is very common, but its large-scale use and association with sexual frequency hasn't been studied much in a scientific way," Eisenberg said.

It is estimated that around 180 million people around the world use marijuana, according to the latest edition United Nation's World Drug Report. But its overall effects on sexual activity have been difficult to determine precisely.

On one hand, there are reports of erectile dysfunction in heavy users and some studies have found reduced sperm counts in men who smoke. On the other hand, some studies suggest that marijuana stimulates regions of the brain which are involved in sexual arousal and activity.

For the study, Eisenberg and Sun analysed data going back to 2002 from the annual US National Survey of Family Growth which contains information regarding family structures, sexual practices and childbearing from a sample designed to represent the demographics of the American population.

The dataset was used by the researchers because it contains information about how many times participants had had sex in the previous four weeks, and also how frequently they had smoked marijuana over the past 12 months.

Around 25.5% of men and 14.5% of women in the analysis reported having used marijuana, and in addition, the researchers found a positive association between frequency of marijuana use and frequency of sexual intercourse.

Overall, marijuana users were found to have 20% more sex than non-users, Eisenberg said, and the positive association between marijuana use and frequency of intercourse was independent of demographic, health, marital or parental status.

Furthermore, the link could still be seen even after accounting for the participant's use of other drugs. According to Eisenberg, this suggests that the positive correlation doesn't simply reflect a general tendency of less-inhibited types, who may be more inclined to use drugs, to also be more likely to have sex.

Interestingly, the frequency of sexual intercourse rose steadily with increasing marijuana use, which hints at a potentially active role for marijuana in fostering sexual activity.

However, Eisenberg stressed that the study does not prove a causal link. "It doesn't say if you smoke more marijuana, you'll have more sex," he said.