I've posted several here before. There was one larger study from the Royal College but I can't find it.

Here are two.

Negative Effects From Psychological Treatments

Adverse effects of psychotherapy: protocol for a systematic review and meta-analysis

You may want to look at sources cited to find out who else has done work on this topic.

I believe part of the problem is the practice of excluding data from the analysis and results for study participants who dropped out or had adverse reactions.