We all know the traits of the classic 'stoner student': poor grades, slow and a lack of work ethic.
Now, a new study has confirmed the stereotype to indeed be true.
Students who smoke high amounts of cannabis have lower grades and perform worse at school, scientists claim.
Researchers observed 1,100 teenagers who had started college in the US with similar rates of academic success over two years.
However, the participants all smoked different amounts of cannabis and consumed various levels of alcohol.
Grade Point Average (GPA) data was tracked for each participant, while their previous exam results were also assessed.