With the root word “cannabinoid” you might think that this system relies on the presence of cannabis itself, but that is not the case. The ECS was named this is because cannabis and its effects were seen first, and the receptors were noticed later.
The endo-cannabinoid system is present without you ever being exposed to cannabis. Your body, on its own, will produce substances called endocannabinoids, which are neurotransmitters that bind to cannabinoid receptors in your nervous system, that act on and change these systems in some way, whether short-term or long lasting.
Cannabis products, like CBD oil, are also absorbed and used by this system.