A new multidisciplinary academic book on TRPG. The editors gathered most of the renown authors in the field to write chapters on TRPG with different disciplinary angles.Bowman, Sarah Lynne, and Andreas Lieberoth. “Psychology and Role-Playing Games.” In Role-Playing Game Studies: Transmedia Foundations, edited by Sebastian Deterding and José P. Zagal. London: Routledge, 2018.
Without conflict of interest, I suggest you ask your college or university librarian to buy it. I did.
A very clear, evidence-based and comprehensive chapter about everything you wanted to know about TRPG and psychology. It is partially readable via Google Books.