Dissociation in its historical definition by Pierre Janet represents splitting the stream of consci- ousness in response to a traumatic event or in hypnosis. Dissociation is traditionally considered an important etiopathogenetic factor of mental diseases and it also explains some psychopatholo- gical phenomena. This mechanism was used definitely for explanation of the group of dissociative disorders. Influence of dissociation was proved also in other psychiatric disorders and the exi- stence of dissociative continuum from normal dissociation to its pathological forms. Also in de- pression some connections are known which point to dissociative components in depressed patients, above all dissociation connected with symptoms of posttraumatic stress disorder, pro- bably often in connection with resistance to pharmacotherapy. In this pilot research we tested 22 patients with recurrent or bipolar depression by means of DES, BDI-II and in this group 11 patients wen also tested with SDQ-20. Psychic dissociation measured by means of the DES score has a median 9.48 that is more than twice as high as dissociation in the normal population. Median BDI-II was 36.5 and it represents major depression. Somatoform dissociation measured by means of SDQ-20 has a median of 28 and is near to the lower limit for dissociative disorders. Correlation between DES and BDI-II is not close but correlation between DES and SDQ-20 is a very close correlation between measured values of psychic (DES) and somatoform dissociation (SDQ-20) and its value being 0.9. For BDI- II>30 (n=16) the median was DES 16.58 and median BDI-II was 40.25. For BDI-II>40 (n=9) median was DES 22.36 and median BDI-II was 45. Along with increasing depression dissociation measu- red by the DES also increases. 3 patients from the whole group (13.6%) probably have criteria for dissociative disorders (DES>25) and it corresponds with findings which prove that 15% of all psychiatric patients have dissociative disorders. Treatment of these patients thus represents a clinical problem which can be resolved only by means of special diagnostic and therapeutic methods also with respect to danger of resistance of treatment in these patients.

        Key words: dissociation, depression, posttraumatic stress disorder, treatment resistance.