Hi yes it's a closed group so you have to request membership! As I'm sure you're aware, Jeff is the leading DP trailblazer in the states and has written two books on the subject. The mission statement of the group is here:
Welcome to the Initiative for Depersonalization Research (IDS) Facebook group. IDS is dedicated to the promotion of ongoing research into Depersonalization/Derealization Disorder (DDD) as well as increasing awareness of DDD through mass media, social media, and regularly scheduled conferences around the world. Our goal is to provide a seamless venue through which information and publicity efforts throughout the world may be shared. IDS is open to all, and educational conferences will be open to health professionals and the general public. All posts will be reviewed for relevance. This is not a place for general questions, advice or comments about personal experience. Many other forums are available for that purpose and we encourage you to use them. Updates about new research or ongoing research, clinical trials, and relevant events are welcome.