A new study has found that people who use cannabis before the age of 18 end up with fewer academic qualifications.
The research tracked more than 6000 young people in New Zealand and Australia through their childhood and teenage years.
It was based on studies carried out by the University of Otago, and in the Australian states of Victoria and Queensland.
Researchers found that young people who used cannabis at an early age were less likely to complete high school, enter university or attain a degree.
The findings also suggest the early use of cannabis has a greater effect on males achieving academic success than on females.