Taking cannabis can lower your IQ and the effects are worse if you’re young, a study has claimed.

Adolescents who use the drug could be putting both their intelligence and mental health at risk, according to researchers at Western University in Canada. The study found that taking cannabis as a teenager was linked with having a lower IQ and the younger the user was when they first tried the drug, the more their intelligence suffered.

The scientists who carried out the research believe that cannabis has a serious effect on brain development. As well as having a negative impact on IQ, the class-B drug also had a detrimental impact on memory, reward processing, visuo-spatial processing and self-referential activity.

The research also found that cannabis could make depression worse.

Dr Elizabeth Osuch, lead author of the study, said: “These findings suggest that using marijuana does not correct the brain abnormalities or symptoms of depression and using it from an early age may have an abnormal effect not only on brain function, but also on IQ.”

Study used scans and genetic tests

The study, published in the journal Acta Psychiatrica Scandinavica, involved looking at people with depression and healthy individuals who did not use cannabis as well as frequent users of the drug. All those participating in the project were given a brain scan plus cognitive, psychiatric and IQ tests.

Genetic testing was also carried out as it has been suggested that those who become depressed from smoking cannabis may be biologically-predisposed to the condition.

The research team found that those who tried the drug at an early age were more likely to have a particular variation of a brain development gene. Now more work will be carried out to find out more about whether people are genetically predisposed to taking cannabis at a young age.

Many parents of teenagers worry that their children may be tempted to experiment with illegal substances, with cannabis being the first drug of choice for many. Talking to your son or daughter about drugs and the risks they pose is vital but you may be concerned that they will hide any substance misuse from you.

Drug testing is one way you can find out whether your teenage child has been taking illegal substances. A home drug testing kit can detect the presence of certain drugs in your teenager’s urine, giving you an accurate result in just five minutes.

For a more in-depth analysis of drug use over a period of time, hair strand tests can pinpoint exactly which substances have been consumed within the last few months. While urine tests will only check what is currently in a person’s system, evidence of any illegal substances will remain in their hair strand indefinitely as it grows.