There's even more tons of research showing positive effects from meditation.

Meditation research generally is low quality, as is suffers from lack of defined methodology, lack of a consensus definition of what meditation is, and the general subjective experience of meditation. (Concretely, if you want to do brain scans on someone meditating, how do you know they're actually meditating? This extends to scans on people who are "experienced practitioners", how do you know they are experienced practitioners?)

Regardless, the vast body of research does not point to negative effects, most point to mild positive effects, and the medical field considers it perfectly safe for healthy people. If you want to use research, don't pick and choose the studies that find adverse effects, look at the overall body of research.