Cannabis-related admissions to general and psychiatric hospitals increased by 90 per cent and 185 per cent respectively from 2008 to 2016, coinciding with a decline in perceived risk of regular use, according to new research.

Bobby Smyth, Anne O’Farrell and Antoinette Daly, writing in the latest issue of the Irish Medical Journal, argue that Ireland is seeing a changing pattern of cannabis use and cannabis-related health harms.

Their study is based on two national population surveys and three national treatment databases, focusing on people under the age of 34. It finds that cannabis is the illegal drug that causes the greatest amount of disability-adjusted years for older teenagers.

It cites research that shows cannabis use appears to contribute to the development of psychosis and that the risk of psychosis increases with higher potency THC, which is the substance in cannabis that causes the intoxication effects.

“Adolescent cannabis use is associated with depression and suicidality in early adulthood,” note the authors. “There is growing evidence that heavy cannabis use during adolescence has a negative impact on cognitive development and functioning.”

The authors cite statistics which show that past-month cannabis use among adolescents and young adults increased after 2011, “coinciding with a decline in perceived risk of regular use”.

The treatment of cannabis use disorders and cannabis-related hospital admissions have “increased significantly” since 2011 as the drug has grown more potent, the report notes.

From 2008 to 2016, there were increases in the rates of cannabis-related addiction treatment episodes among adolescents and among young adults of 40 per cent and 168 per cent respectively. One in 28 young adults was cannabis dependent in 2015.

Cannabis-related psychiatric admissions more than doubled during the period 2011 to 2017, while general hospital admissions “continued their relentless upward trend”.

‘Worrying increase’

“In spite of this increased harm, there was a worrying increase in the proportion of young adults who saw little or no risk in regular cannabis use,” according to the authors.

“This mismatch between a reduction in perceived risk and the growing scientific evidence that cannabis use is associated with multiple risks is a major concern from a public health perspective.

“It suggests that there has been a major failure to communicate risks to the general public.

“Alternatively, it seems possible that the very positive media coverage generated by campaigns which are seeking to persuade politicians and the public that cannabis has substantial medicinal properties are contributing to confusion among the public regarding its many known hazards.”

The authors conclude by stating that a public information campaign is needed to ensure young people are better informed about the risks posed by cannabis, and that doctors need to become more involved in these discussions.