Medical marijuana strains
The genus Cannabis contains two species which produce useful amounts of psychoactive cannabinoids. Cannabis indica produces a higher level of Cannabidiol (abbreviated CBD) relative to THC (the primary psychoactive component in medical and recreational cannabis). Cannabis sativa, on the other hand, produces a higher level of THC relative to CBD.[4]
Medical use of sativa is associated with a cerebral high, and many patients experience stimulating effects. For this reason, sativa is often used for daytime treatment. It may cause more of a euphoric, “high” sensation, and tends to stimulate hunger, making it potentially useful to patients with eating disorders or anorexia. Sativa also exhibits a higher tendency to induce anxiety and paranoia, so patients prone to these effects may limit treatment with pure sativa, or choose hybrid strains.

Cannabis indica is associated with sedative effects and is often preferred for night time use, including for treatment of insomnia. Indica is also associated with a more “stoned” or meditative sensation than the euphoric, stimulating effects of sativa, possibly because of a higher CBD-to-THC ratio
Many strains of cannabis are currently cultivated for medical use, including strains of both species in varying potencies, as well as hybrid strains designed to incorporate the benefits of both species. Hybrids commonly available can be heavily dominated by either Cannabis sativa or Cannabis indica, or relatively balanced, such as so-called “50/50” strains.

Cannabis strains with relatively high CBD-to-THC ratios, usually indica-dominant strains, are less likely to induce anxiety. This may be due to CBD’s receptor antagonistic effects at the cannabinoid receptor, compared to THC’s partial agonist effect. CBD is also a 5-HT1A receptor agonist, which may also contribute to an anxiolytic effect. This likely means the high concentrations of CBD found in Cannabis indica mitigate the anxiogenic effect of THC significantly.[6]