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Marijuana may affect fertility in young men
June 5th, 2014
11:19 AM ET

Marijuana may affect fertility in young men

"If you’re a cannabis user and you’re trying for a baby ... stop."

This advice comes from Dr. Allan Pacey, senior lecturer in andrology at the University of Sheffield in the United Kingdom and lead author of a new study that suggests using marijuana could increase a man's risk of fertility problems.

The study, published in the journal Human Reproduction, looked at how a man's lifestyle affects his sperm morphology: the size and shape of sperm. Researchers collected data from 1,970 men who provided semen as part of a fertility assessment.

All of the lifestyle information was self-reported, and researchers made no attempt to confirm accuracy. Of those men, 318 produced abnormal sperm, where less than 4% of it was the correct size and shape (as defined by the World Health Organization). The remaining men's sperm had a higher percentage at a "normal" size and shape.

"Cannabis smoking was more common in those men who had sperm morphology less than 4%," Pacey said. "Cannabis affects one of the processes involved in determining size and shape. And we also know that the way cannabis is metabolized is different in fertile and infertile men."

The study found that men who had less than 4% normal sperm were typically under 30 years old, had used marijuana within three months of giving their sample and were twice as likely to have provided their sample during the summer.

Any of those factors could have influenced sperm morphology, but Pacey said "the only thing we found that was a risk that a man can do something about was cannabis."

The researchers did not set out to study cannabis; they were simply collecting data about men’s lifestyles to identify risks to fertility. They looked at a number of possibilities, including cigarettes, alcohol, recreational drug use, employment history, BMI, medical history and the type of underwear the men wore. The researchers concluded that none of these were factors.

A third of all infertility cases are linked to the male partner, according to the American Society for Reproductive Medicine (PDF). The society says marijuana is associated with impaired sperm function and should not be used by men trying to conceive.

Society President Rebecca Sokol says the study confirms previous studies that found a possible but not proven link between abnormal semen and sperm function and the use of cannabis. But she warns that the study does not have enough cases to draw definite conclusions.

"The take-home lesson of the article is that clinicians should counsel their patients on the possible relationships between lifestyle factors, abnormal semen parameters and fertility outcomes," Sokol said. "This should include a discussion that the data are often inconclusive, but the motto 'everything in moderation' is a wise approach for the couple who is planning a pregnancy."

Another paper on the health consequences of cannabis was published this week in the New England Journal of Medicine. Dr. Nora Volkow, director of the National Institute on Drug Abuse, and a team of the institute's researchers prepared a paper detailing the risks based on the strongest scientific evidence currently available. According to the paper, they wanted to dispel "the popular notion that marijuana is a harmless pleasure" and does not need to be regulated.

The paper details what the research shows are the adverse effects of recreational use, including the risks of addiction. Approximately 9% of those who try marijuana will become addicted; one in six of those who start as teenagers and 25% to 50% of those who smoke daily become addicted.

The researchers also wrote about the harmful effects of cannabis use on brain development, especially in kids and teenagers. Preliminary research shows that adolescents who are early-onset smokers are slower at tasks, have lower IQs later in life and have an increased incidence of psychotic disorders.

Other problems associated with marijuana use, according to the paper, include impaired short-term memory and motor coordination, altered judgment, effects on school performance, a higher risk of motor-vehicle accidents and higher risk of cancer and other health issues like heart disease and stroke.

"There is a widespread and growing perception among not only youth, but the public in general, that marijuana is a relatively harmless drug, and it has been difficult marshaling science to correct this perception," Volkov said. "The science of marijuana is far from settled, and this has allowed advocates of various positions to cherry-pick evidence to support their particular stance."

The review also lists some of the potential therapeutic benefits of cannabis. Conditions and symptoms that may be helped by marijuana treatment include glaucoma, chronic pain, multiple sclerosis, epilepsy, nausea, inflammation and AIDS-related anorexia and wasting syndrome, according to the report.

Volkow and her fellow researchers fear that as governments begin to modify marijuana policy toward legalization, recreational use will increase, as will a host of negative health problems.

However, Mason Tvert, communications director at the Marijuana Policy Project, says the report by the National Institute on Drug abuse researchers is not an objective review of current scientific evidence.

The Marijuana Policy Project has worked to reform marijuana policies and laws since 1995 at both the federal and state level. It lobbies for legislation that would replace marijuana prohibition in favor of legal regulation. It provided much of the staff and funding in the push to legalize and regulate marijuana for adults 21 and older in Colorado in 2012, and its goal is to pass, by 2017, at least 10 more laws that would regulate cannabis like alcohol.

"NIDA has long been criticized for prioritizing politics over science," Tvert said. "They fail to acknowledge any of the well-known research that refutes, and in some cases completely debunks, their conclusions. This more closely resembles a poorly written college essay ... than it does an objective, evidence-based journal article. Every objective study on marijuana has concluded that it poses far less harm than alcohol to the consumer and to society."


soundoff (131 Responses)
  1. Ulg

    Pffft association- every other cell in the human body has multiple governors to prevent marijuana from harming the cell. For all we know it could that marijuana smokers have a higher predilection to drink mountain dew, or ride a bike.

    June 7, 2014 at 08:49 | Report abuse | Reply
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      June 12, 2014 at 22:24 | Report abuse |
  2. michelle

    if so many pot smoking men carry odd sperm, how come they have such healthy beautiful offspring?? another doctor that thinks he knows everything...... my husband and i smoked our heads off, and have 5 beautiful healthy children/ grandchildren. in yr face science!

    June 7, 2014 at 09:53 | Report abuse | Reply
    • Joe

      I agree with everything you said except calling what this doctor is pushing as science. It's more like a mandate for the drug companies.

      June 7, 2014 at 13:58 | Report abuse |
  3. Jake

    I can not exaggerate enough how much B.S. this article is. Just another last ditch effort to try to make people afaid of cannabis. My dad smoked it for almost 20 years and had 7 kids. My friend smoked it for 9 years and has 4 kids. Please people do not take anything this article says as any type of truth.

    June 7, 2014 at 11:11 | Report abuse | Reply
  4. Joe

    If wiz khalifa, snoop dog, and bob Marley were able to have kids I'm not too worried

    June 7, 2014 at 16:35 | Report abuse | Reply
  5. DailyDinners

    The truth: http://www.budski.net/marijuana-messed-up-sperm/

    June 8, 2014 at 02:51 | Report abuse | Reply
  6. Justin @ Budski.net

    Sorry, here's the actual truth on this http://www.budski.net/marijuana-messed-up-sperm/

    June 8, 2014 at 02:54 | Report abuse | Reply
  7. mililani

    And this is bad news WHY? Fewer baby daddies is a good thing.....................

    June 8, 2014 at 14:01 | Report abuse | Reply
  8. AR

    i survived colon cancer at six years ago, at the age of twenty-four. i've been smoking marijuana since i was 16. i have two sons, five years and ten months old.

    TELL ME that it affects fertility.

    June 8, 2014 at 23:08 | Report abuse | Reply
    • Nonovyerbeezwax

      Sigh. What is such a mystery? Just because you have anecdotal evidence doesn't make your experience statistically significant.

      June 10, 2014 at 07:15 | Report abuse |
  9. radioman961

    Have you followed the work of Dr. Lani Burkman, an andrologist, researcher, professor and now founder of LifeCell Dx? This is going to be a growing issue, along with smoking and use of nicotine products as global birth rates slide. Check out her work and visit: http://www.lifecelldx.com

    Thank you for posting this.

    June 9, 2014 at 10:24 | Report abuse | Reply
  10. Lojack

    How did they "provide semen"? It would take a hot nurse to coax it out of me! (How can I volunteer for one of these studies?)

    June 9, 2014 at 12:14 | Report abuse | Reply
    • Joe http://vapermadness.com/

      Sorry pal it is collected by Bluto the intern.

      July 1, 2014 at 15:20 | Report abuse |
  11. rastafarilove

    look how many kids bob marley had and his bassist in the wailors group has over 40 children and they smoked ganja everyday,so this article is false,rastas have the most children.

    June 10, 2014 at 07:43 | Report abuse | Reply
    • Nonovyerbeezwax

      Got a study to back up your claim? No? I thought not.

      June 11, 2014 at 09:10 | Report abuse |
  12. jzaks

    Even though I smoked a bunch of weed in the 60's and early 70's, I did not have any trouble having children. both of whom are well rounded and very successful with children of their own today. I must have had some quality stuff.

    June 11, 2014 at 09:29 | Report abuse | Reply
  13. fabio

    Your Research isn't accurate, im not saying it wrong. Thats just the honest truth. every human body reacts different to even the slight change of absolutely anything. when it come to this research , yeah there might be a percentage of males with this conflict ofcourse, but theres more important conflicts to worrie about, anyways nothing compared to the percentage of not only males that cannabis this nothing more then just a natural relaxant.

    June 11, 2014 at 10:56 | Report abuse | Reply
  14. Bilsabob

    Really the guy is right but, only for some people as many study's show. Which brings me to my next question about the studies done with harder forms of narcotic derived drugs that have lead to a plethora of health problems and addictions. Why is taking a step down from the consistent use of harder narcotic derived and synthetic pharmaceuticals, causing the same/worse issue's versus something that's a natural alternative with the possibility of having the same potential issue's as our current drugs, really being thought as the worse choice? All studies prove is that for some people effects are different then others, and what can be expected for side effects after prolonged use. If no side effects arise in other patients then they wait to see effects on the public after drug is released, hence a lot of recalls. Are the side effects and/or possible side effects really that much worse then the already current standard given to our patients.? When one med doesn't work, do we not try another? When it comes to our lives we will do anything to live...regardless of side effects, that arose/arise within a few people, that a substance may have caused. Thank you for reading.

    June 11, 2014 at 13:42 | Report abuse | Reply
  15. TC

    That aint true I have been smoking half my age &i have two beautiful sons so all that aint working 4me so hahahahah in your face.

    June 16, 2014 at 13:08 | Report abuse | Reply
  16. Paul Pot

    Can they show us the photos?

    June 16, 2014 at 23:03 | Report abuse | Reply
  17. Juilee

    That's surprising but seriously true. I think people should be aware of the reasons that leads to infertility. This has become one of the major concerns for people today.

    June 18, 2014 at 05:33 | Report abuse | Reply
  18. yettaa

    I am a victim of weed but trying to change and I'm seeking for help too..?

    June 22, 2014 at 18:40 | Report abuse | Reply
  19. sephiroth6d9

    only thing that comes to mind is Snoop's kids Cheech's kids Chong's kids and Paul McCartney's kids all exist all healthy and all had fathers that has and or does smoke a butt load of marijuana

    July 3, 2014 at 08:36 | Report abuse | Reply
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Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.