Haha, please show me those studies? U think think any phd doctor in the university would do a scientific research if the belt increase injuries or not in gymactivities?
Or you mean your own friends studies maybe...
Or maybe you should follow a few courses or read a few books from Stuart McGill (Ultimate Back fitness & Performance, Chapter 6, The Question of Back Belts, page 174-186 or Low Back Disorders, Chapter 10, The Question of Back Belts, page 193-201) who did lots of research on the lower back and is the leading researcher in the field of lower back pain.
Look him up on youtube as well