Could cannabis PROTECT you from a stroke? People who smoke marijuana every day have better blood flow and oxygen to the brain, controversial study claims

• We know THC - the property that makes users 'high' - relaxes blood vessels
• But researchers in Texas examined how THC affects the brain over time
• They found that after 2 months, chronic users had better blood flow to the brain
• It is controversial; other experts warn marijuana carries dangerous side effects

By Mia De Graaf

Cannabis could lower a person's risk of having a stroke, new research claims.

Medical strains of the drug are prescribed across more than half of the United States to treat chronic pain, anxiety and epilepsy.

It is controversial; as more states legalize the drug, scores of medical experts warn marijuana carries other dangerous side effects, and we do not have enough research to be sure of its benefits.

However, a study by the University of Texas at Dallas has found the drug can improve oxygen and blood flow to the brain, reducing the risk of clots that cause a brain attack.

In fact, the research team found chronic cannabis users have the most efficient brain blood flow of all, suggesting their stroke risk is lowest.

The researchers at the University of Texas at Dallas found blood flow in the putamen - an area of the brain associated with reward, learning and habits - was greater in users than nonusers

The findings build on previous studies about marijuana's impact on memory function.

But while many earlier papers concluded cannabis slows memory function, Dr Francesca Filey's research team found the drug to have a positive effect.

'Past marijuana research has shown changes in cognitive functions such as memory and executive functioning,' said lead author Dr Francesca Filbey. 

'Our study seeks to understand the possible neurophysiological mechanisms that may drive these cognitive changes.'

We already know that THC - the property in weed that makes you 'high' - is known to relax blood vessels and alter blood flow in the brain.

However, this study focused on how prolonged THC use might affect the brain's blood flow.

They did this by analyzing the differences in regional brain blood oxygenation and metabolism in chronic cannabis users.

Dr Filbey, director of Cognitive Neuroscience Research in Addictive Disorders at the Center for BrainHealth, led the team in examining 74 users and 101 non-users for 60 days.

All users reported at least 5,000 usages over their lifetime and daily use for 60 days leading up to the study. 

Participants were required to refrain from cannabis for 72 hours before the study to eliminate acute effects of the drug. 

Participants underwent magnetic resonance imaging, and THC metabolite levels were measured using urinalysis.

Filbey and her team found that cannabis users showed higher global oxygen extraction fraction and cerebral metabolic rate of oxygen compared to nonusers. 

That increased the more of the drug they consumed.

They also found that blood flow in the putamen - an area of the brain associated with reward, learning and habits - was greater in users than nonusers.

Increased blood flow in the putamen may either reflect the capacity of THC to dilate blood vessels or the development of additional circulatory pathways.

'Currently, cannabis is the most widely used illicit drug,' Dr Filbey said.

'As it becomes more widely legalized, understanding neurophysiological alterations and its effects on the brain's health and performance are becoming increasingly relevant.' 

Due to the prospective nature of the study, published in the journal Neuropsychopharmacology, researchers cannot say whether cannabis use directly causes the observed changes, or whether other underlying conditions also may be at play.

While the reason for the brain changes related to chronic marijuana use is unclear, Dr Filbey said that these changes may reflect underlying differences in brain tissue metabolic rate.