Boys who smoke marijuana go through puberty earlier but grow more slowly than those who have never smoked the drug according to a study presented today at the European Congress of Endocrinology in Dublin, Ireland. The findings will lead to a better understanding of the dangers of drug abuse on growth and development of children.

Scientists at the Pir Mehr Ali Shah Agriculture University Rawalpindi in Pakistan studied the levels of certain hormones involved in growth and puberty in the blood of 220 non-smoking and 217 marijuana-addicted boys. Levels of puberty-related hormones such as testosterone and luteinising hormone (LH) were increased in the marijuana smokers. In contrast, growth hormone levels were decreased in this group. It was also found that non-smoking boys were on average 4 kg heavier and 4.6 inches taller by the age of 20 than the marijuana smokers.

The research team, led by Dr. Syed Shakeel Raza Rizvi, also looked at the effect of smoking marijuana on levels of the stress hormone, cortisol, in 10 marijuana addicts; they found that marijuana smokers have significantly higher levels of cortisol than non-smokers. Dr Rizvi hypothesises that, ―marijuana use may provoke a stress response that stimulates onset of puberty but suppresses growth rate.

Marijuana is the most widely available illicit drug in Europe, it is estimated that it has been used by 80.5 million Europeans at least once in their life. The latest report from the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) reveals that the highest prevalence of marijuana use is in 15 -- 24 year olds and is significantly higher among males than females. Previous studies have looked at the effect of smoking marijuana in adult rats and humans but this is the first time that the effects have been looked at in pubertal boys.

The research may have a wider impact than just health. ―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,‖ explained Dr. Rizvi.