Jun 05, 2014 10:08 AM EDT By Jaleesa Baulkman, UniversityHerald Reporter

Young men who use cannabis may be putting their fertility at risk, according to a recent study.

Researchers from the United Kingdom found that cannabis affects the size and shape of sperm in young men. However, other common lifestyle factors reported by men, including smoking cigarettes or drinking alcohol, appeared to have little effect.

"Our knowledge of factors that influence sperm size and shape is very limited, yet faced with a diagnosis of poor sperm morphology, many men are concerned to try and identify any factors in their lifestyle that could be causing this," Dr. Allan Pacey, lead author of the study, said in a statement. "It is therefore reassuring to find that there are very few identifiable risks, although our data suggests that cannabis users might be advised to stop using the drug if they are planning to try and start a family."

For the study, researchers compared data collected for 318 men who produced sperm of which less than four percent was the correct size and shape to a control group of 1,652 men with "normal" sperm by medical definitions.

Researchers found that men who Men who produced ejaculates with less than four percent normal sperm were nearly twice as likely to have produced a sample in the summer months (June to August), or if they were younger than 30 years old, to have used cannabis in the three month period prior to ejaculation.

Previous studies have suggested that only sperm with good sperm morphology are able to pass into the woman's body following sex and make their way to the egg and fertilize it. Studies in the laboratory also suggest that sperm with poor morphology also swim less well because their abnormal shape makes them less efficient.

"This research builds on our study of two years ago which looked at the risk factors associated with the number of swimming sperm (motile concentration) in men's ejaculates," Dr. Andrew Povey, researcher, said in a statement. "This previous study also found that there were relatively few risk factors that men could change in order to improve their fertility. "

Dr. Povey and colleagues concluded that there is little evidence that delaying fertility treatment to make adjustments to a man's lifestyle will improve their chances of a conception.

The findings were recently published in the Journal of Occupational and Environmental Medicine.

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