Chronic cannabis users have altered cerebral blood flow and metabolize oxygen at a different rate, new research suggests.
Cannabis is the most widely used illicit drug in the United States, according to data from the 2015 National Survey on Drug Use and Health.
Recently, medical marijuana - which is used for health treatment purposes - has been legalized in a number of U.S. states. Some studies suggest that controlled cannabis use can reduce chronic pain, and Medical News Today have reported on research that linked marijuana with lower stress levels in consumers.
However, medical marijuana has not yet been approved by the U.S. Food and Drug Administration (FDA) as a safe product to use, and some studies suggest that it can have negative effects, such as psychological decline, on long-term users.
Considering the split opinions on the pros and cons of using cannabis, as well as its widespread use both recreationally and for medical purposes, it is important for specialists to gain a better understanding of its effects on the human system.
Dr. Francesca Filbey, the director of Cognitive Neuroscience Research in Addictive Disorders at the Center for BrainHealth at the University of Texas at Dallas, has recently led a new study analyzing the effects of tetrahydrocannabinol (THC), which is the main active substance in cannabis, on the brains of chronic cannabis users.
THC is the ingredient responsible for the feeling of intense wellness that comes with cannabis use. This feeling is linked to the brain's processing of oxygen, so Dr. Filbey and colleagues were quite interested in seeing how, exactly, THC affects the flow of oxygen through the brain, and the brain's use of it.
"Our finding suggests that functional and structural changes that have been reported in the brains of marijuana users may be due to alterations in cerebrovascular function," declared Dr. Filbey for MNT.
The scientists' findings have now been published in the journal Neuropsychopharmacology.
Cannabis use impacts brain's blood flow
To conduct the study, the researchers recruited 74 habitual cannabis users, as well as 101 people who did not use cannabis as a control group. The participants were all matched as closely as possible for age and IQ levels.
The cannabis users were selected based on a reported number of at least 5,000 cannabis usages throughout the participants' lifetime, as well as daily ingestion in the 60 days before they enrolled onto the study.
Before conducting the relevant analyses, the researchers asked the participating cannabis users to abstain from ingestion for 72 hours.
Cannabis use was tested by measuring THC levels in the participants' urine. The psychoactive effects of the drug - altering the participants' brain functions - were monitored using MRI.
Specifically, the researchers looked at:
- global and regional resting cerebral blood flow (CBF), referring to the quantity of blood supplied to the brain, both on the whole and locally
- the oxygen extraction fraction (OEF), which reflects on how much oxygen is delivered versus how much is actually consumed
- the cerebral metabolic rate of oxygen (CMRO2), referring to how quickly oxygen is metabolized in the brain
The researchers found that chronic cannabis users had a higher OEF and CMRO2 than people who did not use cannabis. This means that the brains of users extract more oxygen from the blood and also have a higher blood flow.
Another interesting finding was that, in the case of chronic cannabis users, there was a higher blood flow in the region of the brain called the "putamen," which is known to play a role in the reward system and in creating habits.
According to the scientists, these findings might imply that THC is able to dilate blood vessels, thus increasing blood flow, or that new blood vessels are forged.
'Future studies to look at behavioral impact'
The researchers also report some limitations to their study. For instance, they did not find any sex-specific effects of cannabis use, despite previous studies suggesting otherwise.
Dr. Filbey and her colleagues surmise that this might be due to a disproportionate male-to-female ratio in their population sample, and they urge that future studies should aim to recruit an equal number of male and female participants.
The researchers also added that "[a]lthough we found that CBF was associated with [THC], no other association between measures of cannabis use or IQ emerged."
More research is now needed to highlight the further implications of the current findings. Dr. Filbey told MNT that "future studies should determine how these alterations [of cerebrovascular function] may influence behavior."