Women who didn’t use marijuana reported having sex six times on average during the past four weeks. Women who used marijuana daily had sex 7.1 times on average.

The trend was similar for men. Men who abstained from marijuana said they had sex an average of 5.6 times in the four weeks before the survey, compared with the daily marijuana users who reported having sex 6.9 times, on average.

“We were surprised to see the positive association between users,” Eisenberg said. “This was across the board: marital status, race, none of that mattered.” The study focused on heterosexual sex, and it didn’t explain why there might be a connection between sex and marijuana.