According to a recent study of almost 4,000 teenagers, the long-term effects of cannabis on brain function depends on how early you start taking it.

The study set a range of cognition tests to pupils over the course of four years, starting at age 12 or 13, finding that the teenagers who used cannabis underperformed across the board, particularly on tests that dealt with memory and impulse control. Researchers also noted that, in a year where cannabis use increased, lower test scores were reported both that year and the following year.

The study also looked at how alcohol affects the brain, but did not find the same results for this as cannabis. Senior author Patricia Conrod PhD said: “We were surprised that the effects of cannabis were more pronounced than the effects of alcohol – and we were surprised of the lasting effects.

“Even if a young person reduced their use, you could still see effects from the previous year. It was more than we expected.”

What Did The Research Involve?

Over the course of four years the study looked at 3,826 pupils, beginning in the 7th grade. Every year the students were given computerised tests of their brain function, and then filled in a confidential online questionnaire about their cannabis and alcohol use.

The brain function tests measured:

Working memory. This is your short-term memory, that allows you to remember information for long enough for you to complete a task

Perceptual reasoning. This is how we use our senses to make sense of the world around us

Delayed recall memory. This is slightly longer-term memory than working memory. This is what you can remember after a brief period of distraction.

Inhibitory control. This is the ability to control natural impulses and not respond to stimuli

To measure the impact of alcohol and cannabis on the pupils’ cognitive function, the researchers compared their brain function scores with their reported use of both substances. They then looked at the scores as they changed year on year, and noted how these changes were linked to their use of cannabis or alcohol. This helped them to understand whether the changes in the pupils’ substance use predicted changes in their test results.

The study also took into account other factors such as gender, ethnicity, whether pupils lived with both biological parents and their family incomes.

What Were The Results?

To make it easier to note trends in the results, the researchers listed the results separately for both cannabis and alcohol.

For Cannabis

Pupils who used cannabis more frequently displayed poorer results in their working memory, perceptual reasoning and inhibition control tests than pupils who used cannabis infrequently, or did not use it at all.

Pupils who reported an increase in their cannabis use had poorer delayed memory test results than expected in the same year.

Pupils who reported an increase in their cannabis use had poorer results in inhibition control than expected the following year.

There was a stronger correlation between poor test results and frequent cannabis use in pupils who used more cannabis in early adolescence than in those who used it in later adolescence.

For Alcohol

Pupils who drank more alcohol over the course of the four years were shown to have poorer working memory, perceptual reasoning and inhibitory control.

Changes in alcohol use over time did not seem to affect the results of their brain function tests.

Concerns Over Cannabis Legalisation

This study raises concern for the health and cognitive function of teenagers and adults alike, as cannabis is being increasingly legalised all over the world. It is legal in California, Canada and Uruguay, and available for medicinal purposes in 41 countries. Other countries, including Portugal, Switzerland and the Netherlands, take a liberal attitude that sees cannabis used fairly freely.

Over the course of the study, the number of students who said that they never used cannabis fell from 95.4% to 71% in four years. Of the teenagers who already reported using cannabis, those who said that they did so every day increased from 0.37% to 2% over the course of the study.

This is a concerning trend, as with society becoming increasingly accepting of cannabis, the chances of teenagers getting their hands on it also increases. These results prove that this could be far more damaging for them than for anyone else.

Dr Conrod said “The message to young people who wish to succeed in school and their adult life is that they should do what they can to delay their cannabis use as much as possible.

“A regular cannabis user in the 10th grade was three years behind their peers in their development of inhibitory control and equivalent to their non-cannabis using peers in the seventh grade.”

Researchers want to take this study further in the future, identifying causal factors and investigating how far-reaching these issues are.

Co-author and PhD student Jean-François Morin said: “We also want to identify if these effects on brain development are related to other difficulties such as poor academic performance, neuroanatomical damage, and the risk of future addiction or mental health disorders.”

The Ocean Recovery Centre is available to help anyone struggling with an addiction to cannabis, from teenagers to the elderly. We provide a dedicated rehabilitation programme, held in a secure and comfortable residential centre that allows people to focus solely on their recovery. When dealing with a teenager who is struggling with addiction, a residential setting can be important, as it helps to keep them away from a peer group that may not understand how important it is that they stay away from the substances they are addicted to.

We also provide group and family counselling sessions, to help loved ones to work as a group to create a home setting that will help the person struggling with addiction to slot back into their daily life once they leave rehab. Group sessions also offer a great way to meet and talk to peers, and get a better insight of how addiction can be fought.

Please call 01253 847 553, or text HELP to 83222 to speak with one of our friendly advisors today.

If you are an occasional user of cannabis, it might be in your blood for only 24 hours. People who tend to smoke more regularly, will have the drug in their blood for a longer time

Find out more in our blog How Long Does Cannabis Stay In Your System?

John Gillen - Author - Last updated: December 14, 2021

John is one UK’s leading professionals in the addiction recovery industry. Pioneering new treatment techniques such as NAD+ and ongoing research into new therapy techniques such as systematic laser therapy, John is committed to providing the very best treatment for people throughout the UK and Europe. During his extremely busy schedule, John likes to regularly update our blog section with the latest news and trends in the industry to keep visitors to our site as well informed as possible on everything related to addiction treatment.