Accumulating evidence indicates an impact of childhood adversities on the severity and course of mental disorders, whereas this impact on psychotic disorders remains to be specified. Effects of childhood adversities on comorbidity, on symptom severity of the Positive and Negative Syndrome Scale and global functioning across four months (upon admission, 1 and 4 months after initial assessment), as well as the course of illness (measured by the remission rate, number of re-hospitalizations and dropout rate) were evaluated in 62 inpatients with psychotic spectrum disorders. Adverse experiences (of at least 1 type) were reported by 73% of patients. Patients with higher overall level of childhood adversities (n=33) exhibited more co-morbid disorders, especially alcohol/substance abuse and dependency, and higher dropout rates than patients with a lower levels of adverse experiences (n=29), together with higher levels of positive symptoms and symptoms of excitement and disorganization. Emotional and physical neglect were particularly related to symptom severity. Results suggest that psychological stress in childhood affects the symptom severity and, additionally, a more unfavorable course of disorder in patients diagnosed with psychoses. This impact calls for its consideration in diagnostic assessment and psychiatric care.