SSRI's + MDMA does not cause serotonin syndrome.

Before I start I will say that I AM NOT A MEDICAL PROFESSIONAL, I have just done my research so don't do this because of a post by some random guy that you saw on reddit.

I keep seeing people freak out when someone takes MDMA with an SSRI saying that it will cause SS. The logic behind this is: SSRI's increase the amount of serotonin available in the brain, MDMA releases all of your serotonin, therefor combining the both will lead to excess serotonin levels in the brain causing serotonin syndrome. But this is just something that someone would think of off the top of their head and the pharmacology of drugs is much more complex than most of us know.

"To enter the presynaptic neuron in order to release serotonin, MDMA uses the reuptake protein, which is by definition inhibited by SSRI. No excess of serotonin means no serotonin syndrome" (Sources : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8155739/ https://www.sciencedirect.com/science/article/abs/pii/S0304394009003322 thanks u/Safetweaker). To simplify this, SSRI's block the same protein that MDMA uses to release serotonin into the brain and depending on your dosage of SSRI's and MDMA this can either very from feeling slightly less effects from MDMA from what you would feel normally, to feeling nothing at all. If you search around online for trip reports of people taking MDMA with SSRI's you will find that almost all of them experienced what I described, they didn't die nor did they go through any life threatening incidents, or if they did it wasn't because of the SSRI medication.

There is a paper here, which claims that MDMA when mixed with SSRI's can cause serotonin syndrome but it doesn't say what articles were used and how the researcher came to that conclusion, they essentially just said that a search was done previous articles were looked into. Yet again, mentioning ZERO of the articles that were used and how they came to the conclusion that mixing MDMA + SSRI's causes serotonin syndrome. SEE EDIT.

To conclude, you still shouldn't SSRI's and MDMA but it is still "safe" to do so, you won't die from it nor will you get any serotonin syndrome. But just because you won't die or cause much, if any, damage from doing so doesn't mean that you should, don't do it.

And while it is "safe" enough to mix MDMA with SSRI's it's definitely NOT safe AT ALL to mix MDMA with MAOI's, that is the real danger. don't mistake this post for claiming that its safe to mix other kinds of antidepressants, this post is for SSRI-type medications ONLY, not MAOIs or any other kind of meds.

Edit: debunk of paper mentioned here.

EDIT 2: Study where 10 participants were given an SSRI several days before taking MDMA