Photo by Masha Raymers

Learn | 02.28.2023

What’s The Ideal Age To Start Using Weed?

Research suggests that the legal age to use weed in the U.S. might be unnecessary.

When was your first experience with cannabis? More importantly, how old were you? It’s pretty common to have started using cannabis in your teens

But the age-old question remains, does cannabis use hinder brain development in teenagers? Some studies point out that the legal age for cannabis use in the United States doesn’t have to be 21. If it were a few years earlier, there wouldn’t be much of a difference in long-term brain development.

Still, frequently using cannabis during your teens can lead to long-term effects on the brain. Read on for more information about how weed affects adolescent brains and the ideal age to start using cannabis.

How Does Weed Affect A Young Brain?

Although you might have started using weed in your teens, be it smoking or eating ediles, adolescent cannabis use puts the person at greater risk of developing negative long-term effects.

The most notable long-term side effect of teenage cannabis use is altering the development of the brain. It’s a known fact that the human brain continues developing until the early or mid-20s. 

So, while the brain’s shape changes along with other developments in various regions, a young brain is more at risk of developing long-term side effects of cannabis use since the brain hasn’t reached full maturity. 

More specifically, cannabis use in teens can impact the following brain functions:

  • The shape of the brain
  • Connections between brain regions
  • Neurotransmitter function
  • Brain structure volume
  • Overall decreased cognitive function

What Is The Ideal Age To Start Using Cannabis?

In the United States, the legal age to purchase cannabis is 21 years old. In Canada, the legal age is 19 years old, with the exception of Alberta (18) and Quebec (21). Are these ages representative of the ideal time to start using cannabis?

Interestingly, one 2020 study published in the journal BMC Public Health notes that using cannabis during or after the age of 19 doesn’t put the individual at risk of developing long-term side effects on the brain. Study lead Hai. V Nguyen writes that “Several later life outcomes from starting cannabis use at age 19 are not different than starting at or after age 21.”

So, while the U.S. and the province of Quebec have limited cannabis use to 21 years and older, research proves that using cannabis just a few years before the legal age won’t have more long-term effects than using cannabis at 21.

However, Nguyen also notes that using cannabis before the age of 19 can lead to “significantly worse outcomes” on brain development, including the following:

  • Overall cognitive function
  • The ability to attain, remember, and understand new information
  • Negative mental health susceptibility


For years, society has been told not to smoke weed until you’re in your mid-20s. That’s because, until recently, research has suggested that the brain reaches full maturity near the age of 25.

However, recent studies have pointed out that using cannabis at the age of 19 will not have much more of a negative effect on brain development than smoking weed in your mid-20s. It’s still not suggested to use cannabis before the age of 19, especially frequently.

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