An Otago University researcher says studies of long-term cannabis use beginning in adolescence suggest its harm has been underestimated.
Professor Richie Poulton has conducted at least four studies of cannabis use by New Zealanders born in 1972. About 80% of the sample group had tried cannabis by their early thirties.
He says evidence of gum disease, respiratory disease, reduced cognitive function and greater risk of psychosis shows the drug does more harm than is widely appreciated, although moderate irregular use is not associated with a great deal of harm.
But Professor Poulton says the unlawful status of cannabis gets in the way of conveying sensible health messages about its use.
He says accurate information is hijacked either by those who want to maintain the ban and or by those who say cannabis is harmless.
Professor Poulton says for this reason, researchers like him need to be persistent about getting such information into the policy arena.