The fact cannabis is illegal is a barrier to those people who use it seeking help for detrimental affects the drug may have on them, according to a psychology professor.
Research has found regular cannabis use at a young age can increase the risk of suicide and depression later in life.
Research done by the American Medical Association, which combines 11 studies of more than 23,000 people found the risks are low but the amount of young people using cannabis means there’s potential for a large number to be affected.
Associate Professor Joe Boden from University of Otago told TVNZ1’s Breakfast today information was collected from a number of studies in the US, New Zealand and Australia.
"We were able to find a 37 per cent increase in the risk of major depression and larger increase in risk for suicidal behaviour."
Professor Boden says even when people are arrested for using cannabis it doesn't stop them from using it again.
"The law isn’t really deterring many people, but it is certainly a deterrent to young people getting treatment for problems related to cannabis."
Referring to synthetic cannabis, Professor Boden says with no regulation of cannabis - just its prohibition - and people sometimes are not aware whether they're taking real cannabis or the more dangerous synthetic form.
"There’s absolutely no regulation as to what the content of what a person would buy is, certainly a legalised regime would be a way to tackle that issue."
He says so far there is little evidence to suggest that either decriminisation or legalisation has increased use in young people.
A referendum will be held next year in which New Zealanders can vote on whether they think cannabis should be legalised.