How does acetaminophen reduce pain? Once inside the brain, p-aminophenol meets the endocannabinoid system and interesting things happen. A few months ago, a study discovered an additional mechanism of action; acetaminophen also affects the brain’s other endogenous cannabinoid called 2-AG. These new findings reveal the multiple ways that acetaminophen produces pain relief and suggests potential avenues for future pain relievers. So, could acetaminophen cause autism via these actions in the brain?