Marijuana Might Alter Men's Sperm

Cannabis use by men under 30 doubled odds of abnormal sperm size and shape

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) The effects of smoking marijuana are under careful scrutiny these days. One finding may make young men considering a family think twice before lighting up.

A recent study found that cannabis use by young men may increase the chances of having sperm that are an abnormal shape and size, which could affect fertility.

The study also found that men’s sperm health decreased during the summer months, between June and August.

"Talk with your doctor about infertility concerns."

This study was led by Dr. Allan Pacey, of the Department of Human Metabolism at the University of Sheffield in the United Kingdom.

The researchers asked 2,249 men from 14 fertility clinics around the UK to fill out a detailed questionnaire about their lifestyle and medical history. Of the original men who filled out the questionnaires, reliable data were available on the sperm of only 1,970 men.

Dr. Pacey and team broke the men into two groups based on sperm health. The first group included 318 men who had less than 4 percent of their sperm verified as being a proper size and shape. The remaining 1,652 men had more than 4 percent of their sperm verified as a proper size and shape, which is considered normal under the current medical definition published by the World Health Organization (WHO).

The research team analyzed sperm samples and organized the data based on the men’s lifestyle habits and medical history as disclosed in the questionnaire.

The data showed that abnormal sperm samples were almost twice as likely to be produced during the summer months or from a participant who was under the age of 30 and had smoked cannabis within the last three months.

The authors noted that they failed to find associations between abnormal sperm health and many other lifestyle factors, including cigarette smoking, alcohol use, age, ethnicity and body mass index (BMI).

"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. 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,” Dr. Pacey said in a press release.

The authors acknowledged that their study may have limited by poor participation, possibly caused by participants' desire to avoid having lifestyle decisions more closely investigated.

This study was first published June 5 in Human Reproduction.

The study was funded in part by the UK Health and Safety Executive and the UK Department of Health.

The authors made no disclosures.

Review Date: 
June 10, 2014
Last Updated:
June 11, 2014