Does substance use affect academic performance? Updated

Substance use reduces the academic performance of university students

University of Colorado Denver, USA, and IZA, Germany

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Elevator pitch

A non-trivial portion of traffic fatalities involve alcohol or illicit drugs. But does substance use—which is linked to depression, suicide, and criminal activity—also reduce academic performance? Recent studies suggest that the consumption of alcohol has a negative effect on the grades of university students. Likewise, there is evidence that marijuana use reduces the academic performance of university students. Although students who use illicit substances are more likely to drop out of high school than those who do not, this may reflect the influence of other, difficult-to-measure factors at the individual level, such as personality.

Percentage of US 18- to 20-year-olds who
                        used an illicit drug in the previous month

Key findings

Pros

Several studies provide convincing evidence that alcohol consumption reduces academic performance as measured by grades of university students.

There is reasonably strong evidence that the use of marijuana reduces the academic performance of university students.

Cons

Alcohol use does not seem to appreciably reduce the probability of attending, or graduating from, university; but more research is needed on this topic.

There is evidence, albeit weak, that drinking reduces the probability of graduating from high school.

Illicit drug use by teenagers appears to be unresponsive to policy intervention, and, as a consequence, very little is known about its relationship to important educational outcomes such as dropping out of high school.

Author's main message

To date, researchers have not produced credible evidence that alcohol use affects educational attainment as measured by, for instance, years of education or the likelihood of dropping out of high school. By contrast, the consumption of alcohol appears to negatively impact the grades of university students. Likewise, there is evidence that marijuana use reduces the academic performance of university students. The use of other illicit drugs is correlated with poor educational outcomes, but no causal relationship has been demonstrated as of yet. Illicit drug use by teenagers is generally unresponsive to policy, so credible natural experiments are rare. Without them, the effects of substance use cannot be distinguished from those of personal characteristics.

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