Below is a link to an interesting paper by one Ilona C. Cuddy which Steven Hassan has on his Freedom of Mind website.
Ms. Cuddy apparently wrote this as part of her Master's Thesis "in partial fulfillment of the requirements for the degree of Master of Mental Health Counseling at Cambridge College Cambridge, Massachusetts."
In addition to discussing how dissociative disorder is a common occurence among cult members in general, she mentions JWs specifically in the body of her paper:
An Independent Research Project
Abstract: Cults have become a phenomenon in our world today. There are thousands of members in the United States alone. Ex-members exhibit symptoms of posttraumatic stress due to the use of mind control techniques which are used within the cults. 10 ex-members of cults were sought out through the internet to participate in a survey which was designed to assess whether ex-cult members suffer from symptoms of posttraumatic stress. The 4 page survey consisted of three parts; history, symptoms, and treatment. Age of involvement was usually early twenties and thirties. Subjects reported having a religious preference, several had close friends and most had up to 3 years of college education. The majority of subjects experienced a predominant loss prior to joining the cult. A few had traumatic experiences preceding membership. Subjects did not display posttraumatic stress disorder prior to joining a cult unless they had experienced a trauma. Ex-cult members clearly showed that dissociative symptoms are central to the cult experience. Almost all subjects sought multiple treatments for recovery. These included; psychotherapy, individual and group, medication, pastoral counseling and exit counseling. - [Emphasis added]