Hippocampus and cognitive domain deficits in treatment-resistant schizophrenia: A comparison with matched treatment-responsive patients and healthy controls.

Some patients with schizophrenia do not respond to pharmacotherapy. More severe cognitive dysfunctions have been associated with treatment-resistant schizophrenia (TRS). This study examines cognitive functions and hippocampal volumes in 43 patients with TRS and compared them to 43 treatment-responsive patients (NTRS), matched on age, sex and education, as well as 53 healthy controls (HC). The results showed that there were significant deficits in all domains of cognition and hippocampal volumes in TRS as compared to HC group. However, TRS specific deficits, as indicated by comparisons with matched NTRS, were limited to poorer performance in working memory (p = 0.003) and smaller total hippocampal volume (p = 0.01). Logistic regression analysis showed that working memory deficits [OR 0.94 (95% CI 0.89-0.98), p = 0.005] and smaller hippocampal volume [OR 0.89 (95% CI 0.81-0.97), p = 0.01], but not their interactions (p = 0.68), contributed to higher risk of treatment resistance. The findings suggest that treatment-resistance to currently available antipsychotic medications may not be due to global cognitive deficits in these patients, but be associated with specific deficits in working memory and hippocampus deficits in the subgroup of schizophrenia.