Boys who smoke cannabis before puberty could stunt their growth by four inches

Study also found link between early onset of puberty

Boys who smoke cannabis before puberty could stunt their growth by up to four inches in comparison with their non-smoking counterparts, a new study has suggested.

Research led by Dr Syed Rizvi from the Pir Mehr Ali Shah Agriculture University in Rawalpindi, Pakistan, associated cannabis users with reduced levels of growth hormones.

His team analysed blood samples taken from 437 boys, 217 of whom were habitual cannabis-users before reaching puberty. They found those who smoked the drug were also more likely to hit puberty prematurely.

Furthermore, they were more likely to weigh four kilograms (8.8lbs) less than non-cannabis users by the age of 20. Saliva samples also found that that levels of the stress hormone cortisol were significantly higher among boys who smoked.

The study concluded: "Marijuana use may provoke stress responses resulting in stimulation of pubertal development and suppression of growth rate.

"Early puberty is associated with younger age 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."

Additional reporting by PA