Dissociative disorders and other psychopathological groups: exploring the differences through the Somatoform Dissociation Questionnaire Perturbações dissociativas e outros grupos psicopatológicos: explorando as diferenças através do Somatoform Dissociation Questionnaire (SDQ-20)A b s t r a c t Objective: The Somatoform Dissociation Questionnaire is a self-report questionnaire that has proven to be a reliable and valid instrument. The objectives of this study were to validate the Portuguese version and to determine its capability to distinguish patients with dissociative disorders from others with psychopathological disorders. Method: 234 patients answered the translated version of Somatoform Dissociation Questionnaire. The Portuguese Dissociative Disorders Interview Schedule was used to validate clinical diagnosis. Patients with dissociative disorder (n = 113) were compared to a control group of 121 patients with various anxiety and depression disorders. Results: Reliability measured by Cronbach's α was 0.88. The best performance of the Portuguese form was at a cut-off point of 35, which distinguishes between dissociative disorder and neurotic disorders with a good diagnostic efficacy (sensitivity = 0.73). The somatoform dissociation was significantly more frequent in dissociative disorder patients, conversion disorder patients and post-traumatic stress disorder patients. Conclusions: These findings suggest that dissociative disorders can be differentiated from other psychiatric disorders through somatoform dissociation. The Portuguese version of the Somatoform Dissociation Questionnaire has fine psychometric features that sustain its cross-cultural validity. Descriptors: Somatoform disorders; Dissociative disorders; Psychiatric disorders; Hysteria; Validation studiesResumo Objetivo: O objetivo deste estudo foi adaptar, validar e determinar a confiabilidade da versão portuguesa do Somatoform Dissociation Questionnaire e determinar a sua capacidade de discriminar doentes que dissociam de outros doentes. Método: O Somatoform Dissociation Questionnaire foi traduzido para o português e retrovertido para o inglês de forma a garantir a sua base conceitual. Os sujeitos responderam também à versão portuguesa do Dissociative Disorders Interview Schedule de forma a validar o seu diagnóstico clínico. O estudo incluiu 234 sujeitos divididos entre 113 doentes com patologias dissociativas e 121 doentes com outras patologias do foro ansioso e depressivo. Resultados: O Somatoform Dissociation Questionnaire versão portuguesa mostrou o seu melhor desempenho no ponto de corte 35, apresentando uma sensibilidade de 0,73. O alfa de Cronbach revelou uma consistência interna de 0,88. A dissociação somatoforme foi significativamente mais freqüente nos doentes com patologias dissociativas, patologias conversivas e distúrbio de stress pós-traumático. Conclusões: A versão portuguesa do Somatoform Dissociation Questionnaire mostrou-se um instrumento útil para discriminar doentes com patologia de foro dissociativo de outros doentes.