In spite of good development of laboratory and instrumental methods of diagnostics of brain and mental disorders, there remains an insufficiency of methods for etiology differentiation, especially clinical-psychopathological in psychiatry.

is to evaluate the differential diagnostic's opportunities in estimation of clinical phenomena's complexity for identification of neurotic, organic or endogenous genesis of disorders.

expert estimation, statistical.

As the experts 7 certified specialists (psychiatrists, psychologists and others) were involved.

In the research the academically definitions and the clinical case descriptions of the following clinical phenomena were estimated:

1. - Conversion, obsession, neurasthenia, phobia, derealisation/depersonalization, anxiety (partly specific for neurotic, stress-related and somatoform disorders);

2. - True hallucinations, confusion, amnesia, fixation hypomnesia, anecphoria (partly specific for organic mental disorders);

3. - Pseudo hallucinations, delusion of control, automatism, paralogia, emotional withdrawal, autism, ambivalence (common symptoms of schizophrenia);

4. - Inability to feel, sadness, lassitude, euphoria, excitement as the signs of endogenous affective disorders.

5. - Mainly non-specific phenomenon - persecutory delusions.

Thus were obtained 14 estimates for each item on a 100-point scale.

Dispersion of majority ranges was too high to get significant differences. But 6 from 7 experts significantly (p<0.05) and 1 tendentionally (p<0.01) rated 3 symptoms (autism, conversion and paralogia) as relatively more complex as compared with 7 more simplex phenomena (anxiety, confusion, euphoria, excitement, neurasthenia, phobia and sadness) by U-Wilcoxon-Mann-Whitney criteria.

established ranges of psychopathological phenomena's complexity reveal non-linear relations to etiology but in some cases they can be useful instrument of differential diagnostics of mental disorders.