Coffee affects your metabolism in dozens of other ways besides waking you up, including your metabolism of neurotransmitters typically linked to cannabis, a study reports. The neurotransmitters related to the endocannabinoid system — the same ones affected by cannabis — decreased after drinking four to eight cups of coffee in a day. That’s the opposite of what occurs after someone uses cannabis. The study also gives possible insight in the cause of munchies. Coffee may also increase the elimination of steroids.