I can believe "a small U.S. community study" got 1.5%, although I would sure like to know which community, and when, and what their criteria were!
The one that says "may" and "perhaps" is softening it to the point of being meaningless, ugh.
Okay, looks like I ended up with the second edition (1996) of Ross's 1989 book. It doesn't have the exact lines you quoted, but it has follow-ups! A more-developed iteration of the research with the University of Manitoba students:
Ross, C. A., Ryan, L„ Voigt, H., & Edie, L. (1991). High and low dissociators in a college student population. Dissociation, 4, 147-151
"Ross, Ryan, Voigt, and Edie (1991) administered the DES to 345 college students in Winnipeg, then gave a battery of further measures including the DDIS to 22 students scoring under 5 on the DES and 20 scoring above 22.6. The high scorers were selected by starting with the highest DES score in the sample of 345 students, and working downward until 20 subjects had consented to complete the follow-up battery. High and low DES scorers differed at very high levels of significance on all measures: Of the 20 subjects scoring above 22.6 on the DES, 14 (70%) met DDIS criteria for a dissociative disorder including 8 with DID." (109-110)
So there's the 1-in-50 estimate. 8/345 = 2.3%. But the book itself spells out that the DES and the DDIS are both screening tools, not diagnostic tools. This is "2% of subjects should definitely get psychiatric follow-up to explore if they have DID," it's still a step behind "2% of subjects definitely have DID."
Aaaand here's Ross's switch point between 1989 and 1992!
"To date, only one study has attempted to determine the lifetime prevalence of the dissociative disorders in the general population (Ross, 1991a)." (108)
The 1% DID rate is his interpretation of the results of that study...though he goes into a bunch of detail about the limits and caveats. None of which show up later when he's doing pithy quotes for forewords, which is a shame.
I was going to edit this into the post, but I should probably c&p entire passages and make a whole follow-up post at this point, huh?
One last note here, though -- Ross comes up with a distinct category of "severe DID" -- and says, again from the 1991 study, "no such cases were detected in a sample of 502 respondents" (109).
Not totally sure what his criteria are. I infer/hope it's informed by his experience with patients! And along with more studies of the "people who meet the DDIS criteria for recommended DID screening" rate, we could really use some studies big enough to measure the "people who meet the Ross criteria for severe DID" rate.
Re: Dammit Erin you nerdsniped us
The one that says "may" and "perhaps" is softening it to the point of being meaningless, ugh.
Okay, looks like I ended up with the second edition (1996) of Ross's 1989 book. It doesn't have the exact lines you quoted, but it has follow-ups! A more-developed iteration of the research with the University of Manitoba students:
Ross, C. A., Ryan, L„ Voigt, H., & Edie, L. (1991). High and low dissociators in a college student population. Dissociation, 4, 147-151
"Ross, Ryan, Voigt, and Edie (1991) administered the DES to 345 college students in Winnipeg, then gave a battery of further measures including the DDIS to 22 students scoring under 5 on the DES and 20 scoring above 22.6. The high scorers were selected by starting with the highest DES score in the sample of 345 students, and working downward until 20 subjects had consented to complete the follow-up battery. High and low DES scorers differed at very high levels of significance on all measures: Of the 20 subjects scoring above 22.6 on the DES, 14 (70%) met DDIS criteria for a dissociative disorder including 8 with DID." (109-110)
So there's the 1-in-50 estimate. 8/345 = 2.3%. But the book itself spells out that the DES and the DDIS are both screening tools, not diagnostic tools. This is "2% of subjects should definitely get psychiatric follow-up to explore if they have DID," it's still a step behind "2% of subjects definitely have DID."
Aaaand here's Ross's switch point between 1989 and 1992!
"To date, only one study has attempted to determine the lifetime prevalence of the dissociative disorders in the general population (Ross, 1991a)." (108)
The 1% DID rate is his interpretation of the results of that study...though he goes into a bunch of detail about the limits and caveats. None of which show up later when he's doing pithy quotes for forewords, which is a shame.
I was going to edit this into the post, but I should probably c&p entire passages and make a whole follow-up post at this point, huh?
One last note here, though -- Ross comes up with a distinct category of "severe DID" -- and says, again from the 1991 study, "no such cases were detected in a sample of 502 respondents" (109).
Not totally sure what his criteria are. I infer/hope it's informed by his experience with patients! And along with more studies of the "people who meet the DDIS criteria for recommended DID screening" rate, we could really use some studies big enough to measure the "people who meet the Ross criteria for severe DID" rate.