Let’s talk about 5-HTP. Chances are, if you’ve ever rolled on MDMA with people who know what they’re doing, you’ve likely been told to reach for a tiny vial of 5-hydroxytryptophan, or 5-HTP, the morning after. The compound treats the emotional hangover by restoring the brain’s stores of serotonin, the “happiness hormone” (not actually a hormone) that’s released when the drug kicks in. This is not flimsy, druggy science. It works and it’s available in your local drug store and, yeah, you should probably grab some.

First, let’s consider how MDMA gets you high in the first place. When you take MDMA — or ecstasy, or molly — the soaring euphoria you feel is your neurons opening their floodgates to allow stockpiled serotonin to pour out. With serotonin molecules floating around in the spaces between brain cells, they’re free for receptors on adjacent cells to grasp at, like a volley of baseballs into a field of gloves. The magic happens once the molecules are caught.

Serotonin is a signaling molecule. When enough receptors on a neuron manage to catch it, the neuron “fires,” kicking off an electrical chain reaction of signaling throughout the brain’s network of cells that eventually results in the happiness, empathy, sociability, and heightened sense of touch associated with rolling on MDMA. Eventually, the molecules are released, and they’re collected back by the cells they were first ejected from, where they’re broken down by an enzyme called monoamine oxidase. The wave of “happy” signaling ceases until a new trigger releases another flood of serotonin.

This is, on some level, happening in the brain all the time, only on a much smaller scale. The crazy thing about MDMA is that it releases an abnormally huge amount of serotonin at once, so it’s more likely that, coming back to the baseball analogy, our neurons’ gloves will have multiple baseballs to catch (yes, I know that’s not how baseball works), and thus continue to send euphoria-making signals through the brain. But because serotonin is degraded by cells when it’s been taken back in, and isn’t produced quickly, drug users risk running low. That deficit is ultimately what causes the post-MDMA sads.

This is where 5-HTP comes in. It’s one of the major ingredients the body needs to make serotonin in the first place, so we take it in hopes that it’ll make it easier for the brain to replenish its stores after releasing them in an MDMA-fuelled free-for-all. When it enters our serotonin-producing brain cells, an enzyme snips off the “P” in 5-HTP, leaving behind a molecule known as “5-HT,” or 5-hydroxytryptamine. Which is the chemical name for — you guessed it — serotonin.

In theory, it makes a lot of sense to take some after a night spent rolling. And there’s plenty of anecdotal evidence to suggest that it works in practice, although the scientific data backing that up is relatively scarce. That’s not to say that 5-HTP doesn’t help; it more likely just indicates that science isn’t particularly interested in it. As one 2002 study put it, 5-HTP is probably better, at least, than placebo at treating depression (which is, in many cases, also an issue of serotonin depletion and reuptake), but because alternative antidepressants exist, 5-HTP’s usefulness is “limited at present.”

Sold in delis and drugstores in tablet or liquid form, the substance is usually extracted from the seeds of an African shrub called Griffonia simplicifolia. Its associated side effects — nausea, heartburn, gas, and, in some people, feelings of fullness and rumbling sensations — are pretty benign. (It does, however, get complicated if you’re already on SSRIs for treating depression.) Keep in mind that if it does work, it’s not going to bring your mood back up to an MDMA-level high; all it can do, hypothetically, is bring your serotonin levels back to the status quo. Triggering the release of that serotonin is all on you.