Objectives

Schizophrenia (SZ) is a chronic mental illness characterized by a combination of positive, negative, and cognitive symptoms. Dual disorders, like the concurrence of SZ and substance-use disorder (SUD), often lead to poorer outcomes compared to SZ alone. This study aims to characterize and compare basic memory processes (encoding, storage, and retrieval) in three groups: patients with SZ without SUD (SZ-), patients with SZ and SUD (SZ+), and patients with only SUD.

Material and methods

A total of 175 male patients undergoing treatment were included in the study: 50 with SZ-, 50 with SZ+, and 75 with SUD. Patients with SUD were abstinent for 3 to 12 months, while those with SZ were clinically stabilized. Memory was assessed using the Rey Auditory Verbal Learning Test (RAVLT), and the Vocabulary subtest of the WAIS-IV was used as a covariate to control for educational level in the statistical analyses (MANCOVA). Additionally, clinical variables were collected to assess their potential interactions with memory performance.

Results and conclusions

The preliminary findings indicate that all three groups scored significantly below normative population data on the RAVLT, suggesting cognitive impairment across the sample. The SZ+ group showed the most impaired memory performance, followed by the SZ- group and then the SUD group. Significant differences between the groups were also observed in all three memory processes: encoding, storage, and retrieval.

These results underscore the negative impact of dual diagnosis on neurocognitive functioning, particularly memory processes, in patients with SZ. This study highlights the need for targeted interventions to address cognitive deficits in individuals with SZ, especially those with comorbid SUD. The findings have important implications for the clinical management and treatment of individuals with SZ+.