The legalization of the recreational use of marijuana for adults 21 and over allows for people to possess the drug in some U.S. states. However, a much impressionable and younger crowd of pot smokers is growing (to an extent) — teenage boys. In a study presented at the European Congress of Endocrinology in Dublin, Ireland, researchers at Pir Mehr Ali Shah Agriculture University Rawalpindi in Pakistan found boys who smoke marijuana through puberty will stunt their growth due to a decrease in growth hormone levels.

In the U.S., an estimated 12 percent of eighth graders reported using the drug in the past year while seven percent of these students are currently using it, according to the National Institute on Drug Abuse. Young people may believe marijuana is a safe drug because of its medicinal uses, legal status, and because it’s “natural,” although not everything that is natural is good for you, like tobacco. On average, there is about 10 percent THC (delta-9-tetrahydrocannabinol) in today’s marijuana.

"Early puberty is associated with younger age of onset of drinking and smoking, and early matures have higher levels of substance abuse because they enter the risk period at an early level of emotional maturity,” said Dr. Syed Shakeel Raza Rizvi, lead author of the study, in the news release.

The growing concerns over the effects of marijuana use on teens, surrounds the developing brain. The mind-altering drug can disrupt the transition that takes place form the brain of a child into the brain of an adult by suppressing neurons in the hippocampus and causing learned behaviors to deteriorate. A 2010 study published in the journal Clinical EEG and Neuroscience found the use of marijuana during the teen years negatively impacted brain structure volume, quality of white manner, and the ability to perform cognitive function.

Now, Rizvi and his colleagues sought to analyze the effects of marijuana use among pubescent boys. They assessed puberty and growth-related hormones in the blood of 220 non-smoking and 217 marijuana-addicted boys. The research team also examined the levels of the stress hormone cortisol through collecting saliva samples among 10 adult marijuana users.

The findings revealed levels of puberty-related hormones such as testosterone and luteinizing hormone (LH), increased among marijuana smokers. However, growth hormones decreased in this group. When researchers checked back in with the men at age 20, the non-smokers were on average 4 kilograms (9 pounds) heavier and 4.6 inches taller than their marijuana-smoking counterparts.

The researchers were also able to trace the added cause of stress in the body and found marijuana boosted cortisol levels among marijuana addicts. "Marijuana use may provoke a stress response that stimulates onset of puberty but suppresses growth rate," Rizvi said.  

Previously, marijuana has been linked to psychosis and its ability to induce anxiety rather than cure it. A 1988 study published in The Journal of Clinical Psychiatry found people who have a tendency to have panic disorders were more likely to experience worse anxiety when smoking weed. This suggests the therapeutic effects of marijuana on someone who suffers from anxiety can widely vary.

However, Marijuana use has been able to show promise regarding other types of physical and mental health problems. The strain of marijuana, known as “Charlotte’s Web,” which is high in cannabidol (CBD) and low in THC, has provided a variety of results when it comes to suppressing seizures in animals, while human testing is still in development. Recently, a study presented at the American Academy of Neurology's annual conference found the extract CBD can potentially become a treatment for children with severe epilepsy due to its ability to reduce the number of seizures by half.

Recreational use of marijuana among teens can alter brain function, but its medicinal use may be able to save the lives of severely ill children. The effects of marijuana vary based on its use from person to person.

Sources: Rizvi SSR et al. Smoking marijuana may cause early puberty and stunts growth in boys. European Society of Endocrinology. 2015.

Jacobus J, Squeglia LM, and Tapert SF. The Influence of Substance Use on Adolescent Brain Development. Clin EEG Neurosci. 2010.

Campos PE, Pontius EB, and Szuster RR. Marijuana sensitivity and panic anxiety. J Clin Psychiatry. 1988.