A new study shows cannabis use impacts not just people's lungs but also their hearts

Research in The Journal of the American Heart Association shows cannabis use is associated with a high risk of a heart attack and stroke - and that risk increases with higher usage.

The latest NZ Health Survey found about eight percent of 15 to 24-year-olds use cannabis weekly and 24-percent use it at least monthly.

Asthma and Respiratory Foundation Chief Executive Letitia Harding says there's a perception among many that it's not harmful.

She says this study shows that actually it looks like it does do damage to the heart as well as to the lungs.