Cannabis users typically associate a different profile of experiences with indica and sativa strains, attributing mellowing properties to the former and an invigorating effect to the latter. This trend continues into the scientific literature: a 2019 study of medical marijuana patients found that patients experienced more symptom relief from indica products compared to sativa or hybrids. What accounts for this difference in subjective effects?
Scientists have debated whether cannabis indica is its own species or rather a subspecies of cannabis sativa for centuries, with some maintaining that the two belong to one species and others arguing that there are as many as four species of the plant. While a 2005 study of cannabis samples from around the world found that the strains were distinct enough in their genetic code and geographical origin to justify consideration as their own respective species, there is no known chemical unique to either indica or sativa. Instead, the distinction between the strain is visual, defined by plant height, leaf shape, and other factors.
In a 2016 interview for the academic journal Cannabis and Cannabinoid Research, former President of the International Cannabinoid Research Society gave the following comments about common beliefs regarding different strain properties:
The sativa/indica distinction as commonly applied in the lay literature is total nonsense and an exercise in futility. One cannot in any way currently guess the biochemical content of a given Cannabis plant based on its height, branching, or leaf morphology.
Dr. Anthony Russo, M.D.
Although the varieties are not defined by chemical content, it’s possible that sativa products are more likely to have contain certain compounds and indica products are more likely to have others.
The main active ingredients in cannabis are the two major cannabinoids: tetrahydrocannabinol (THC) and cannabidiol (CBD). These act on the body’s endogenous cannabinoid system, primarily by binding CB1 and CB2 receptors to trigger cellular effects. However, multiple studies have ruled out a significant difference in THC and CBD content between indica and sativa strains as a whole, leading scientists to consider the contributions of other compounds like terpenes.
Terpenes are volatile organic compounds found in cannabis and other compounds. WHile they are responsible for the distinct aroma of the drug, they have garnered increased recognition among the scientific community in recent years for their role in the drug’s psychoactive properties. These compounds are thought to modulate the effects of cannabinoids, a phenomenon known as the “entourage effect”. For example, D-limonene is thought to enhance the anti-anxiety effects of CBD by enhancing dopamine and serotonin signalling, while β-myrcene complements the pain relief associated with CBD and THC by stimulating the release of naturally occurring opioids in the body.
In the study of medical marijuana patients, researchers acknowledged that they relied on self-reported data, meaning they could not control for the chemical makeup of the cannabis products and only had information about whether the participant was using indica or sativa. It is possible that the difference in symptom relief the indica users experienced was due to increased occurrence of relevant terpenes in indica strains.
Professionals and researchers in the cannabis field advocate for a departure from the indica/sativa dichotomy in characterizing the effects of cannabis. These individuals recommend that broader chemical compositions of an individual strain to be made known to the public so that cannabis consumers can make more informed health decisions.