Examining the validity of the assessment of Gender Identity Disorder : Diagnosis, self-reported psychological distress and strategy adjustment
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AbstractTranssexualism is characterised by a discrepancy between biological sex and gender identification, in spite of hormonal levels that are normal with respect to the biological sex. Generally, having the diagnosis ‘transsexualism’ or ‘Gender Identity Disorder’ (GID) is a prerequisite for hormonal and surgical treatment. Since transsexualism is such a rare phenomenon, and a so-called ‘gold standard’ against which the diagnosis could be evaluated is lacking, it is of utmost importance that reliable information be published by as many clinics as possible. One of the main aims of this thesis in psychiatry was to investigate potential differences in diagnostic ‘habits’ or interpretation of the classification rules as provided by DSM-IV and ICD-10 among four European GID clinics (Belgium, Germany, the Netherlands and Norway). Secondly, it was investigated whether a widely used self-report inventory, the SCL-90-R, is suitable to be used in this patient group as well as two other patient groups. Finally, it was investigated whether cross-sex hormone therapy in GID patients has an effect on the answering strategy they employ on a math test that is known to show sex differences. The diagnostic criteria were interpreted in a similar manner in the four clinics. However, a distinction was made in Amsterdam between onset/duration on the one hand and severity/persistence on the other hand. This may lead to differences in diagnostic decisions among the clinics. It is recommended that severity and duration be taken into account in the next version of the DSM. The findings of two of the papers suggest that the dimensionality of the SCL-90-R is not stable. Subscale scores be used with care in patient groups reporting little distress, such as GID patients. Finally, it is concluded that even though cross-sex hormone treatment has been shown to not influence cognitive performance as such, it may still influence other cognitive factors, such as answering strategy and adjustment.
List of papers. Papers I and IV are removed from the thesis due to copyright restrictions.
Paper I: Paap, M. C. S., Kreukels, B. P. C., Cohen Kettenis, P. T., Richter-Appelt, H., de Cuypere, G. and Haraldsen, I.R. Assessing the Utility of Diagnostic Criteria: A Multi-Site Study on Gender Identity Disorder. The Journal of Sexual Medicine, 2011, Volume 8, Issue 1, pages 180 190. doi:10.1111/j.1743-6109.2010.02066.x
Paper II: Paap, M. C. S., Meijer, R. R., van Bebber, J., Pedersen, G., Karterud, S., Hellem, F. and Haraldsen, I. R. A study of the dimensionality and measurement precision of the SCL-90-R using Item Response Theory. Submitted version, published in: International Journal of Methods in Psychiatric Research, 2011, Volume 20, Issue 3, pages e39 e55. doi:10.1002/mpr.347 The definitive version is available at www3.interscience.wiley.com
Paper III: Paap, M. C. S., Meijer, R. R., Cohen Kettenis, P. T., Richter-Appelt, H., de Cuypere, G., Kreukels, B., Pedersen, G., Karterud, S., Malt, U. F. and Haraldsen, I. R. Why the factorial structure of the SCL-90-R is unstable: comparing patient groups with different levels of psychological distress using Mokken Scale Analysis. Psychiatry Research Volume 200, Issues 2 3, 30 December 2012. doi:10.1016/j.psychres.2012.03.012
Paper IV: Paap, M. C. S. and Haraldsen, I. R. Sex-based differences in answering strategy and the influence of cross-sex hormones. Psychiatry Research, 2010, Volume 175, Issue 3, pages 266-270. doi:10.1016/j.psychres.2009.07.020