Hi there! It is true that CBD (and THC) can impede the metabolism of many drugs, including SSRIs, that may possibly lead to an overly-high serum level of the SSRI, which can possibly lead to serotonin syndrome. However, that would take a very high amount of CBD—much higher than you should be taking for depression or anxiety.
The cytochrome p450 system accounts for 70 to 80 percent of the enzymes involved in drug clearance, making it the most important system for drug metabolism. Both THC and CBD are competitive inhibitors of three different enzymes in the cytochrome p450 system, two of which are involved in the metabolism of SSRIs. This means that CBD and THC are competing for the same receptors as is the SSRI. So, when an SSRI is taken concurrently with CBD and/or THC, the SSRI serum concentration could possibly rise since CBD is competing for the same receptors for metabolism, which may lead to serotonin syndrome. https://ghr.nlm.nih.gov/primer/genefamily/cytochromep450 I hope this helps!