Chronic marijuana smoking affects brain chemistry, decreasing the number of cannabinoid CB1 receptors, a new study involving molecular imaging has shown.
The CB1 receptors are involved in not just pleasure, appetite and pain tolerance but also a host of other psychological and physiological functions of the body.
"Addictions are a major medical and socioeconomic problem," says Jussi Hirvonen, lead author of the collaborative study."
Unfortunately, we do not fully understand the neurobiological mechanisms involved in addiction. With this study, we were able to show for the first time that people who abuse cannabis have abnormalities of the cannabinoid receptors in the brain," he added.
As a part of the study, researchers recruited 30 chronic daily cannabis smokers who were imaged using positron emission tomography (PET), which provides information about physiological processes in the body.
They were injected with a radioligand, 18F-FMPEP-d2, which is a combination of a radioactive fluorine isotope and a neurotransmitter analog that binds with CB1 brain receptors.
The results showed that the receptor number was decreased by about 20 pc in the brains of cannabis smokers. These changes were found to have a correlation with the number of years a subject had smoked.
"This information may prove critical for the development of novel treatments for cannabis abuse. Furthermore, this research shows that the decreased receptors in people who abuse cannabis return to normal when they stop smoking the drug," Hirvonen explained.