Final answer:
Marijuana use increases appetite by stimulating the hormone Ghrelin. THC, a cannabinoid in marijuana, is known to affect appetite regulation, leading to what is colloquially known as "the munchies".
Step-by-step explanation:
Marijuana use temporarily increases appetite by stimulating the effects of d) Ghrelin. Ghrelin is a hormone that signals to the brain when the stomach is empty, thus promoting hunger. On the other hand, Leptin is a hormone that signals satiety when the stomach is full, leading to a reduction in hunger. Studies have shown that THC, one of the main cannabinoids found in marijuana, can increase appetite in patients. This increased appetite while under the influence of marijuana is often referred to as "the munchies" and is a well-documented effect of THC on the brain's appetite regulation.
By contrast, neurotransmitters such as serotonin often have an inhibitory effect on eating. However, when it comes to the psychoactive effects of marijuana and appetite stimulation, THC's interaction with ghrelin plays a more central role.