Ever worried that your jobless, stoner boyfriend was going to knock you up and stay in your life forever? Well, you can cut the paranoia, because a new study has shown that smoking weed doubles the risk of male infertility and increases the chances of producing abnormal sperm.

The good news for broody stoner dudes is that if you quit for three months, your sperm production cycle will start afresh and you can get planning that family. According to Dr Allan Pacey, who authored the study in scientific journal Human Reproduction: "You've got to stop in June to see an improvement in August."

We conducted a study of our own called "Looking at Bob Marley's Wikipedia Page" and this is what we found: "Bob Marley had a number of children: three with his wife Rita, two adopted from Rita's previous relationships, and several others with different women. The Bob Marley official website acknowledges eleven children."

That's not to say that Dr Pacey's study isn't correct. His team analysed sperm samples from 318 men who volunteered information about their eating, drinking and drug taking habits and the overwhelming statistic was the cannabis factor.

“We found that cannabis doubled the risk of men under 30 having poor sperm," Dr Pacey told the Independent. "Statistically it jumped out of the analysis. I think it’s a real effect, and it’s not been shown before in such a robust way."

Disclaimer: getting the bong out is not a contraceptive.