The Wikipedia page on DSM-5 says that the American Psychiatric Association (APA) mandated that DSM-5 task force members sign a nondisclosure agreement (NDA). What was APA's public rationale behind this NDA?
The National Institute of Mental Health Data Archive (NDA) makes available human subjects data collected from hundreds of research projects across many scientific domains. The NDA provides infrastructure for sharing research data, tools, methods, and analyses enabling collaborative science and discovery. De-identified human subjects data, harmonized to a common standard, are available to qualified researchers. Summary data is available to all.