According to a recent neuroimaging study, the human cannabinoid receptor 1 (CB1 receptor) gene is sensitive to positive emotional stimuli. The effects are greater in some people than in others where a particular variation of the gene is found. In other words, people in whom the variant of the gene is more often active are generally happier most of the time. The same gene is responsible for the euphoric effects associated with an intake of marijuana.
The study was carried out by researchers based in Japan and led by Masahiro Matsunaga. Dr. Matsunaga is a leading researcher at the Department of Health and Psychosocial Medicine at the Aichi Medical University School of Medicine.
The Medical Marijuana Review contacted Dr. Matsunaga to find out more about the study. According to the scientist, the motivation for the research was that “studies have suggested that the human endocannabinoid system is associated with positive emotional processing.” This led to an examination of cannabinoid receptors in the brain.
To measure the effects of the human cannabinoid receptor 1 gene, Dr. Matsunaga explained, the team measured happiness levels among 198 individuals. The analysis revealed that those who carried a variation of the gene were happier than the average. The study also found that the group carrying the variation had a higher sensitivity to positive emotional events (that is, they got more out of “something special,” such as an event or watching a movie, than the average person). Presence or absence of the variation was shown through genetic testing.
The variation of the gene is termed a “polymorphism.” This is a reference to certain point mutations within a genotype, and it is not something that occurs in all people. Typically, with the human cannabinoid receptor 1 gene, people carry a thymine-thymine (TT) genotype, whereas a minority of people have a cytosine (C) allele.
Dr. Matsunaga’s study was designed to see if “C allele carriers evaluated their current mood state more positively.” The basis was that “happiness is one of the most fundamental human goals” and this “led us to examine the source of individual happiness.”
The 198 participants were required to assess their own “levels of happiness.” In noting their state of happiness, each individual completed questionnaires after watching a “happy” movie (what Matsunaga termed “a subjective evaluation”). The questionnaires were evaluated using a Japanese version of the Subjective Happiness Scale (JSHS), a tool developed by psychologists to assess well-being. Like height or temperature or IQ, happiness is said to lie on a continuum and researchers use a numerical scale to evaluate it. The scale ranges from very, very low to very, very high.
Scientists are of the view that there are two states of happiness: a temporary emotional state (hedonia) and a relatively stable state of being happy (eudaimonia). What interested Dr. Matsunaga most was eudaimonia, the stable state of happiness, and exploring why some people, apparently carrying the genetic variant, seem to be happy most of the time.
To show the connection between the gene and a feeling of happiness, the scientists scanned the brains of individuals with the variant gene using a technique called neuroimaging. Neuroimaging uses techniques to image the structure and function of the brain. The technique used in the study was positron emission tomography (PET scan). A PET scan detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body via a biologically active molecule.
Using the sophisticated scanning tool, Dr. Matsunaga and colleagues observed higher levels of activity in brain areas that regulate positive feelings, with positive emotion-related brain regions such as the medial prefrontal cortex showing signs of significant activity. The researchers found a positive correlation between the subjective feeling of happiness and the specific mutation in the human cannabinoid receptor 1 gene. These people were “more prone to the effects of cannabinoids … in turn, positive emotions offer one explanation as to why individuals with the polymorphism are generally happier.”
The receptor gene is triggered by cannabinoids (specific chemicals that activate the pathways). Cannabinoids can be produced naturally by the human body or absorbed through the smoking or ingestion of marijuana. The “happiness gene” and the marijuana compounds affect the CB1 receptor. These receptors are highly concentrated in the brain and act to alter appetite, pain, mood and memory. Research has suggested that the CB1 receptor is involved in the maintenance of homeostasis in health and disease.
Thus, the research showed that the human cannabinoid receptor 1 gene encodes for the CB1 receptor along the same pathway in the brain responsible for the marijuana “high.” Marijuana contains over 80 different cannabinoids, of which tetrahydrocannabinol (THC) is present in the greatest concentration and functions as the principal psychoactive constituent of marijuana. Just as THC, via CB1 activation, indirectly increases dopamine release and produces psychotropic effects, so too does the variant gene to produce an ongoing effect of “happiness.”
While the study did not specifically look at the effect of marijuana consumption on levels of happiness, the fact that the same receptor is triggered either naturally in the body or through the intake of marijuana is of great interest. The findings partly explain the euphoric experience associated with marijuana smoking, and this is likely to be a subject of further study.
The results of the study have been published in the journal PLOS ONE, titled “Genetic Variations in the Human Cannabinoid Receptor Gene Are Associated with Happiness.” The research was funded by the Japan Society for the Promotion of Science.
The researchers may continue with the examination of how the cannabinoid system affects mood, although their next area of research will be a psychological study into exploring why a certain smell evokes a specific memory.
Photo courtesy Flickr user Arbri Shameti