I just looked this up on Wikipedia the other day. I was surprised to learn that this study has recently been discredited.

> Rosenhan’s paper continues to be cited hundreds of times a year, and its alleged findings are seen as crucial evidence of psychiatry’s failings. Yet based on the findings of an investigative journalist, Susannah Cahalan, and on records she shared with the author, we now know that this research is a spectacularly successful case of scientific fraud.

0. https://journals.sagepub.com/doi/10.1177/0957154X221150878