Marijuana Slows Boys’ Growth But Causes Early Puberty

Most adolescents can’t wait for the physical signs of maturity to start, including height and curves in the right places. But a new study found that boys who smoked marijuana were on average 4.6 inches shorter and nearly 9 pounds lighter by age 20 than non-smoking boys.

Consuming pot not only slowed boys’ growth, but also triggered the onset of early puberty, the researchers reported. And early puberty has been linked with greater substance abuse, the study authors noted.

In what was billed as the first study of marijuana use by actual boys during puberty, the findings were recently presented at the European Congress of Endocrinology held in Dublin, Ireland. Scientists at Pakistan’s Pir Mehr Ali Shah Agricultural University Rawalpindi reported that growth hormones were lowered and puberty hormones were higher among 217 boys who used marijuana than among 220 boys who didn’t smoke pot.

“It was also found that non-smoking boys were on average 4 kg (8.8 pounds) heavier and 4.6 inches taller by the age of 20 than the marijuana smokers,” the researchers wrote.

Dispelling the “Mellow Stoner” Stereotype

The study team, led by Syed Shakeel Raza Rizvi, PhD, looked at hormone levels in blood samples of the adolescent boys. Puberty-linked hormones such as testosterone and luteinizing hormone were elevated in the marijuana smokers. Researchers also conducted a micro study on what it called “10 marijuana addicts” from the same sample group of 217 users. The team examined marijuana impacts on cortisol, the so-called stress hormone. Despite the “mellow stoner” stereotype, marijuana was found to increase the stress hormone.

Dr. Rizvi theorized in the study’s conclusions that “marijuana use may provoke a stress response that stimulates onset of puberty but suppresses growth rate.”

Marijuana’s Reach

Why this may be important is partly a matter of global scale:

Marijuana is the most commonly used illicit drug in Europe and in the United States, especially among teens and younger adults.

In Europe, the study reports that 80.5 million Europeans have used marijuana at least once in their life. The latest report from the European Monitoring Centre for Drugs and Drug Addiction shows that marijuana use is most common in those aged 15 to 24 years old. Males are “significantly higher” users than females.

In the U.S., beyond pot being the most frequently used illicit drug, the National Institute on Drug Abuse 2014 survey found that overall drug abuse was down, with decreased use of alcohol, cigarettes and prescription pain relievers, as well as decreased use of inhalants and synthetic drugs such as synthetic marijuana, also known as K2 or Spice.

There was, however, no rise in pot use despite it being legalized in more states. The survey noted a change in attitude about marijuana: a drop in viewing the drug as harmful and in overall disapproval. Still disturbing were the results in surveying thousands of adolescents: Nearly 12 percent of 8^th graders had smoked marijuana in the last year and 6.5 percent were current users.

As parts of the U.S. legalize marijuana for medical use and it’s been found to help symptoms of conditions such as post-traumatic stress disorder that other drugs haven’t reduced, research on its damage to adolescents has emerged. Recent studies have shown that even once-weekly marijuana use alters still-developing brains in a variety of ways that include long-term memory problems.

Pot and Early Puberty

Marijuana’s active ingredient is tetrahydrocannabinol (THC). It causes symptoms of psychosis, anxiety and depression, and may aggravate existing psychiatric disorders. While it’s considered less addictive than alcohol or tobacco, addiction treatment doctors say patients may develop psychological dependence on marijuana.

The European study linked marijuana to provoking earlier puberty, and early puberty is associated with drinking and smoking at a younger age. Rizvi said “early matures” experience higher levels of substance abuse simply because their emotional maturity hasn’t caught up with their physical development.

Nancy Wride

Follow Nancy on Twitter at @NWride