Young teenagers who become hooked on cannabis may be causing lasting damage to their memory, intelligence, and attention, a long-term study says.
Experts from Britain, the US and New Zealand found that those who had regularly used the drug when they were under 18 suffered a drop in IQ.
“The adolescent brain is particularly sensitive to the negative effects of substances like cannabis,” said Richie Poulton, Health Research Director at Otago University in Dunedin, New Zealand.
“IQ is important for all sorts of things in life. It predicts how well you do educationally, then predicts how well you do in the job market. It also predicts how you end up health-wise.”
More than 1,000 people from Dunedin took part in the study over more than 20 years. The results of regular cannabis users were compared with those who didn’t indulge.
Pro-cannabis activists, in favour of legalising the drug, are concerned about how the results might be interpreted.
“Hopefully the message that cannabis can be harmful for some young people if they use too much of it, too early, doesn’t get turned around into a, you know, cannabis blows your brain for everyone…,” said Abe Gray of the National Organisation for the Reform of Marijuana Laws in New Zealand.
Cannabis campaigners may be encouraged by another aspect of the study – indicating that heavy pot use after 18 appears to be less damaging to the brain.