Different Plant Origins
Both hemp oil and medical cannabis oil come from a species of plant called cannabis sativa. Humans have farmed cannabis sativa for thousands of years1. Early civilizations selectively bred plants with certain traits, and, over time, this produced a number of distinct strains within the species.
Strong, tall plants were grown to make food and textiles; today this strain is known as hemp. Flowering plants with psychoactive properties were grown for recreational and medical purposes; this strain is commonly referred to as medical cannabis, marijuana or simply cannabis.
Hemp oil is made from hemp plants which have a high fibre content and very low concentrations of pharmacologically active compounds (cannabinoids). Medical cannabis oil comes from cannabis plants with large, cannabinoid-containing flowers, but very little fibre2.
Seeds vs. Flowers
In addition to being sourced from different strains of cannabis sativa, hemp oil and medical cannabis oil are made from different parts of the plant. Hemp oil comes from the seeds of the hemp plant, similarly to almond, flaxseed or sunflower oil, whereas medical cannabis oil is most commonly made from the flowering head of the cannabis plant. Medical cannabis oil can also be produced from cannabis leaves and stems, however the flowering head contains the highest concentration of cannabinoids2.
In most countries, growing hemp is restricted to plants with less than 0.2% THC (tetrahydrocannabinol), the psychoactive compound in cannabis4. Moreover, research has shown that the seeds from which hemp oil is produced contain no cannabinoids at all3. Therefore, hemp oil is not useful for medical purposes and does not cause psychoactive effects.
However, hemp oil does have nutritional benefits. It is made up of more than 80% polyunsaturated fatty acids, and the ratio of omega-6 to omega-3 in hemp oil is considered optimal for health5.
On the other hand, medical cannabis oil contains high concentrations of pharmaceutically active cannabinoids. Cannabis plants contain approximately 400 chemical compounds, 60 of which are cannabinoids6. THC and CBD (cannabidiol) are the most abundant cannabinoids; the exact proportions present in the oil will depend on the variety of plant from which it was extracted.
One exception of note is CBD oil derived from hemp plants. This is generally produced in countries where growth of medical cannabis is restricted, but CBD is not legally controlled. As other parts of the hemp plant such as leaves and stems can contain small amounts of the non-psychoactive cannabinoid CBD (cannabidiol), these may be used to create a pharmaceutically active oil referred to as hemp oil or simply CBD oil.