My understanding is that the interaction between Mitragynine and SSRI's should be pretty negligible. There are examples out there of certain Opioids being potentiated by SSRI's but that is more coincidental than a likely occurrence. Otherwise, Mitragynine seems to be not much more than a standard Opioid agonist of mild-moderate potency. I'm not immediately aware of any Opioid agonists that are commonly used that are dangerous in combination with SSRI's.