Schizophrenia is heterogeneous and often disabling a disease that affects 1% of the population. Current psychopharmacological treatment significantly eliminates the presence of positive symptoms (especially delusions and hallucinations) and partly also negative symptoms (social withdrawal or abulia). In contrast, the cognitive deficits associated both with schizophrenia and depression are only limitedly influenced by pharmacological treatment.The cognitive impairment represents an important part of schizophrenia symptomatology and it has a severe negative impact on patients' quality of life. In depression is the impairment milder but still significantly contributes to patients' daily functioning. The profound deficit was repeatedly documented in the area of declarative and working memory. In this study, we study the effectiveness of virtual environment rehabilitation program focused on declarative memory, working memory and attention in comparison to standard paper-pencil rehabilitation led by an occupational therapist.

This study compares effectiveness of the virtual environment cognitive rehabilitation program with standard paper-pencil approach in within-subject design.

Participants with a diagnosis of schizophrenia, schizoaffective disorder or major depressive disorder will undergo a baseline assessment of cognition.

The participants will be at the baseline randomly assigned to each condition: virtual environment rehabilitation or paper-pencil rehabilitation. Then they will participate in 10-15 sessions (30-45 minutes) once or twice a week.

All participants will undergo retest assessment of cognition.

After completion of the first program the participants will be assigned to the different condition: to paper-pencil or virtual environment rehabilitation. After 10-15 sessions in the second condition the participants will once more undergo retest assessment of cognition.

Within-subject design is an effective tool in the development of scientifically proven treatment tools. This approach allows to obtain reliable information about the effectiveness of the method and to examine the influences of other variables (Steingrimsdottir and Arntzen 2015). This study will allow to get credible information on the importance of using the virtual environment in the context of cognitive rehabilitation in patients with schizophrenia and depression.

Inclusion Criteria:

• Diagnosis of schizophrenia and other primary psychotic disorders or diagnosis of major depressive disorder according to International Classification of Diseases-11

Exclusion Criteria:

• Severe visual impairment
• Age over 60 years
• Diagnosis of other psychiatric disorder than schizophrenia or major depressive disorder
• Physical handicap preventing the participant from participating in virtual environment training
• Refusal to sign an informed consent