Does cannabis lower your IQ? According to a recent study published in the American Journal of Psychiatry, the answer is yes. According to the research, if you consume from childhood to midlife, your IQ lowers by 5.5 points. You also have memory and attention problems.

But how accurate are these findings?

Conflicting Studies

Many studies have focused on cannabis and IQ. A 2001 study found no relationship between cannabis smokers and cognitive impairment. A 2005 study concluded the same thing.

Then some studies suggest the opposite. These studies often point to a smaller hippocampus in long-term users as proof that cannabis lowers your IQ.

The new study, which followed nearly 1,000 individuals in New Zealand from age 3 to 45, concludes that future research is needed to establish causation. 

Does A Smaller Hippocampus Lower Your IQ?

Does Cannabis Lower Your IQ?

The hippocampus is the region of the brain responsible for learning and memory. We have two hippocampi, one for the left side of the brain and one for the right. The hippocampus plays a significant role in consolidating short-term memory into long-term memory. It is also crucial for spatial navigation.

In a famous study, neuroscientists discovered that London cab drivers had an exceptionally large hippocampus due to their ability to navigate 25,000 complex city streets from memory.

Researchers wanted to figure out the chicken and the egg problem. Does having to navigate London’s busy streets cause the hippocampus to grow? Or do people with a larger hippocampus become successful cab drivers? 

Grey Matter Connection

Assuming the most recent study is accurate, and that long-term cannabis use does decrease your hippocampus – does it matter?

Scientists associate a smaller hippocampus with a higher risk for dementia and Alzheimer’s. But it is also possible to grow your hippocampus through exercise and eating foods high in omega-3 fatty acids.

But research suggests the size of your hippocampus isn’t as crucial as the hippocampus’ connectivity and ability to communicate with other brain regions. And this improves through spatial training, such as memorizing and driving around London’s busy city streets. 

A growing number of neuroscientists are starting to recognize what the research is saying. Changes in grey matter brain volumes and white matter work together to optimize cognitive function. Gray matter stashes neurons in specific brain regions, while white matter facilitates communication between different areas. 

So Does Cannabis Lower Your IQ?

So does cannabis lower your IQ or not? If the most recent study is accurate, it appears that if you begin in childhood and smoke well into your midlife, your hippocampus will be smaller than those who didn’t consume for all those years. 

Of course, this is the result of the one study, and even it concluded more research was needed to establish causation.

But assuming the results are confirmed, what’s the difference between cannabis and other activities or lifestyle choices that will result in cognitive decline later in life? 

And what if one combines cannabis with exercise, meditation or yoga? Do the activities that increase the size of the hippocampus offset the potential damage cannabis does? Will a cannabis smoker who is physically active and eats healthy have a better outcome than a non-consumer who eats junk and never exercises?

And say a long-term cannabis user does have a smaller hippocampus. What does that tell us about their brain’s functional connectivity?

Easier for the corporate press to run the headline, “Cannabis Lowers your IQ,” than to question the epistemology of the research.