Those who use the drug as teens struggle with reasoning, memory, and inhibitions in later life
- Teenagers were asked to rate their cannabis use on a zero to five scale, zero meaning 'never' and five being 'every day'
- They were then tested in four cognitive domains: recall memory, working memory, perceptual reasoning and inhibition
- Adolescents who used cannabis the most performed the worst on these tests
- Pot use in any given year was linked to impaired inhibitory control and working memory one year later
Teenagers who use cannabis are inflicting long-term damage on their brains, a new study has warned.
Researchers tracked nearly 4,000 teenagers over fours years and found clear evidence of marijuana use being linked to struggles with reasoning, memory and inhibitions later in life.
Previous studies have shown that cannabis misuse has been linked to impairments in learning, attention, and decision-making, as well as lower academic performance.
But the team, led by the University of Montreal in Canada, says its findings are the first to show the causal and lasting effects of teen pot use on cognitive development.
Researchers say marijuana use in teenagers was linked to struggles with reasoning, memory and inhibitions later on life
For the study, the team followed more than 3,800 Canadian adolescents between seventh and 10th grade for a period of four years.
Once a year, the participants rated how much they used cannabis on a zero to five scale - zero meaning 'never' and five being 'every day'.
For alcohol specifically, the teens were asked to provide the typical number of drinks they have in a day.
Researchers also looked at year-over-year changes in four cognitive areas: recall memory, working memory, perceptual reasoning and inhibitions.
Tasks included being able to find a phone among a group of images, learning a pattern and being able to reproduce it 30 minutes later, and completing a sequence of puzzles with increasing difficulty.
The number of students who reported never using cannabis fell from 95.4 percent in the first year of the study to 71 percent in the last year.
Meanwhile, teens who reported using marijuana every day increased five-fold from 0.37 percent in year one to two percent in year four.
Using an advanced analytical model, the study found that teens who used cannabis more frequently performed the worst on the cognitive domain tests.