Issues of the schizophrenia comorbidity and concurrent ingestion of psychoactive substances are currently quite topical. In relation to this, we use the term of toxic psychosis, which may be understood also as a nosologically independent group (André et al., 2006), when it correspondents with schizophrenia only partially and for a certain specific period of time. Often, in clinical practice we come across reclassification of this diagnosis into another, so-called functional psychosis from the circle of schizophrenia (Caton, 2005; Drake, 2005; First, 2005). An important role in the comorbidity etiopathogenesis is played by several factors, as a result of which several hypotheses have been developed, e.g., a self-medication hypothesis, biological mechanisms overlapping and genetic sensitivity hypothesis, etc. The ingestion of psychoactive substances in case of schizophrenia deteriorates, according to Koob (1992), positive symptoms of schizophrenia, increases the risk of relapse and thereby also of rehospitalizations, leads to a more frequent non-compliance (Dóci, 2002). Effects of negative symptoms of schizophrenia are not definite (Garaj and Garajová, 2009). Negative effects of comorbidity on an increase in aggressiveness, rise of depressive symptoms, including suicidal acts, have also been confirmed. Currently, complex treatment of comorbidity implemented by a joint team of specialists focusing on both components (treatment of schizophrenia and harmful ingestion or abuse or addiction symptom) using psychopharmacological as well as psychosocial procedures appears to be most suitable.

Key words: schizophrenia - comorbidity - psycho active substances