Does smoking pot cause man boobs?

Many plastic surgeons tell men with gynecomastia, or "man boobs," to stop smoking pot.

Story highlights

  • "Man boobs" result from a hormone imbalance between estrogen and testosterone
  • Animal studies have shown marijuana ingredients can affect testosterone
  • A link between the condition and marijuana use appears plausible
A young man in his 20s -- let's call him George -- sits across from me in the exam room.
"Dr. Youn," he says, "I have man boobs."
I notice a not-so-unfamiliar smell wafting from his body. It's the same odor that floated my way during a rock concert I recently attended.
"How long have you had a problem with this, George?"
"Hard to say. But it seems to have gotten worse over the past year or so."
"George, the first thing you need to do is stop smoking pot. Marijuana could be causing your man boobs."
Gynecomastia, otherwise known as man boobs (or moobs for short), is a condition that affects approximately 33% to 41% of men between the ages of 25 and 45. It's even more common during puberty, affecting 60% of 14-year-old boys. Interestingly, it also affects 55% to 60% of men aged 50 and older.
Dr. Anthony Youn
Although most cases of gynecomastia resolve spontaneously within a few months to a few years, in 2012 nearly 23,000 people underwent surgery to correct the condition. According to the American Society for Aesthetic Plastic Surgery (ASAPS), it was the fifth-most common cosmetic surgery in men.
Gynecomastia is caused by a hormone imbalance between testosterone and estrogen. When the ratio between testosterone and estrogen tips in favor of estrogen, the body responds by creating excessive breast tissue. Hence, man boobs.
Animal studies have shown that exposure to the active ingredient in marijuana can result in a decrease in testosterone levels, a reduction of testicular size, and abnormalities in the form and function of sperm.
In humans, the effects of marijuana on testosterone and estrogen levels aren't as clear. Lower testosterone levels have been reported in chronic marijuana users compared to nonusers, but not all studies support this.
Few studies have examined a direct causative effect between smoking marijuana and gynecomastia. A report in 1972 made the initial connection between cannabis and gynecomastia. This study is contrasted with a 1977 survey of U.S. Army soldiers which showed no association between smoking marijuana and gynecomastia. This study was limited, however, due to its very small sample size.
The legalization of marijuana in some state could make it easier for researchers to determine the exact effects of cannab