Purpose. In this article, we want to show to the reader (both with the thorough literature review, and with presentation of two clinical cases from our own practice), what might be the objective difficulties in differential diagnosis between primary depersonalization-derealization disorder (DPD, code 6B66 according to ICD-11, F48.1 according to ICD-10) and schizotypal disorder (STD, code 6A22 according to ICD-11, F21 according to ICD-10), what may be the cause of these difficulties, and how can a psychiatrist still distinguish between these disorders in his everyday clinical practice.
Methodology. First, we turned to well-known and scientifically respectable DPD monographs, in particular to the Daphne Simeon’s book «Feeling Unreal: Depersonalization Disorder and the Loss of the Self» and to the Maurizio Sierra’s book «Depersonalization: A New Look at a Neglected Syndrome», and to similarly respected monographs on STD, in particular «Schizotypy: New dimensions» by Oliver Mason and Gordon Claridge, and «Schizotypal Personality» by Adrian Reine, as well as to the relevant sources which were cited by these authors in respective chapters of their books.
Then we searched for other relevant articles on the topic of interest, with the use of keywords such as «depersonalization disorder», «schizotypal disorder», «differential diagnosis», in the international scientific databases PubMed, Google Scholar, Web of Science, Elsevier ScienceDirect, Elsevier ClinicalKey.
The literature data we have found were then analyzed, summarized and presented in this article, together with a thorough description and clinical and psychopathological analysis of two clinical cases from our own practice.
Results. The data we have obtained while writing this literature review, as well as our own clinical experience, presented there in the form of a thorough description of two cases from our own practice, in our opinion, convincingly indicate that the differential diagnosis between primary DPD and STD is sometimes difficult. Nevertheless, such differential diagnosis is not only possible, but also necessary. In the field of psychiatry, making the correct diagnosis is also of great practical importance for choosing the correct strategy and tactics of treatment, both psychopharmacological and psychotherapeutic.
Our data also convincingly indicate that, unfortunately, in Russia and post-Soviet countries, overdiagnosis of STE is extremely common in cases where the patient actually has primary DPD, or depersonalization-derealization syndrome (DP/DR syndrome) within the clinical picture of some other mental disorder (usually from an anxiety disorders spectrum or from affective disorders spectrum), as well as a misunderstanding of what the DP/DR syndrome is, what are the typical symptoms and phenomenology of it, together with underestimation of its importance in the overall clinical picture of any given mental disease, underestimation of the importance of specific measures to eliminate the DP/DR syndrome in a given patient, and insufficient ability of specialists to diagnose and treat this devastating syndrome. In light of this, we believe that the material presented in this article is of particular relevance and importance for Russian and other post-Soviet countries’ psychiatrists.
Practical implications. In our opinion, the results we have presented in this review deserve the widest possible application in psychiatry.