Occasional Cannabis Use Doesn't Impair Physical Health Of Young Adults, Twin Study Confirms

How does occasional cannabis use affect our health?
A frequent question, for which there is no simple and conclusive answer. The impact on our overall physical and mental health has yet to be fully researched. The federal status of cannabis as a Schedule I drug severely limits scientific studies on this important topic.

Thankfully, with legalization sweeping across the nation, we are beginning to get some answers on this powerful, mysterious and inspirational plant. 

One study published in the journal Drug and Alcohol Dependence analyzed the connection between marijuana use and physical health among 308 sets of twins. Among other things, the research revealed the often associated connection between marijuana use and reduced exercise and appetite loss is more driven by genetic and environmental factors rather than weed use, writes PsyPost. 

Jessica Megan Ross, the study's author, and her team analyzed data from a co-twin control study conducted among identical and fraternal twins. A co-twin study enables scientists to control shared genetic and environmental factors in its analysis. The data came from an ongoing study called the Colorado Adoption/Twin Study of Lifespan Behavioral Development and Cognitive Aging (CATSLife), which followed 208 pairs of twins from infancy to adulthood. 

 “Understanding the impact of cannabis use on physical health is an important public health concern because the extant literature has reported mixed results,” said Ross, an assistant professor at the University of Colorado Anschutz Medical Campus. “The changes in legalization of cannabis use throughout the United States has been associated with increases in adult cannabis use. However, we still do not have a clear picture of how cannabis use impacts physical health.”

Genetics Play Important Role 

Researchers looked at their subjects' frequency of cannabis use and health status by measuring blood pressure, heart rate and pulmonary functions, to name a few. They also gathered data on exercise frequency and eating habits. Taking into account important parameters, such as inter and intra-family effects, the authors suggested that some people may be genetically predisposed to consume marijuana while at the same time predisposed to exercise less and more frequent appetite loss. 

This means that increased cannabis use in adolescence isn’t necessarily the cause of less exercise in adulthood or that frequent cannabis use in adulthood is related to more frequent appetite loss. 

 “We examined whether cannabis frequency is associated with physical health outcomes phenotypically and after controlling for shared genetic and environmental factors via a longitudinal co-twin control design. We also conducted the exact same analyses with tobacco frequency and physical health to provide a comparison. In general, the results of this study do not support a causal association between using cannabis once a week (the mean cannabis frequency of the sample in adulthood) and detrimental physical health effects of individuals aged 25-35,” Ross told PsyPost.

Another important finding was a causal relationship between marijuana use and resting heart rate, but researchers further noted that this may be due to a lower BMI in the sample that was much lower than the national average.

Ross warned that the study results should not be generalized to the entire US population. “It is important to keep in mind that these results apply only to adults (ages 25-35) who use cannabis, on average, once a week. These results do not apply to adolescents or adults who use cannabis more frequently.” 

She further highlighted that researchers do not suggest that marijuana is safe for everyone. “Although we did not find that cannabis use (once a week) is associated with detrimental physical health effects, people can still develop other negative outcomes from use like cannabis use disorder.”

Other Experts Agree 

Dr. Nora Volkow, director of the National Institute On Drug Abuse (NIDA) discussed the benefits and harms of cannabis consumption in an interview with FiveThirtyEight wherein she acknowledged that there is no scientific evidence that occasional and moderate cannabis consumption is harmful.

“There’s no evidence to my knowledge that occasional [adult] marijuana use has harmful effects. I don’t know of any scientific evidence of that. I don’t think it has been evaluated,” said Volkow, a psychiatrist, in the November interview. ”We need to test it.”

Volkow added that she is concerned about higher rates of marijuana use and that frequent (daily) consumption, in the long run, can produce “harmful effects even on the adult brain.” 

Photo: Courtesy of bruce mars on Unsplash