Antipsychotic dose is not associated with cognitive function in patients with schizophrenia aged under 40: a cross-sectional observational study with retrospective dose estimation

This study aimed to examine the relationship between antipsychotic dosage and cognitive performance in young patients with schizophrenia. A relatively homogeneous sample was selected to reduce clinical heterogeneity and improve sample comparability. In this cross-sectional observational study, psychotic symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS), and cognitive performance was evaluated with the Montreal Cognitive Assessment (MoCA) in clinically stable patients with schizophrenia under the age of 40 who were followed at a Community Mental Health Center. Total antipsychotic dose was calculated using olanzapine equivalents, and 1-year cumulative exposure was estimated using the mg×day formula. Both frequentist and Bayesian analytical approaches were applied. No significant correlations were found between either daily or cumulative antipsychotic doses and MoCA scores (r = 0.067; p = 0.675; BF₁₀ = 0.260; and r = 0.028; p = 0.864; BF₁₀ = 0.554, respectively). Longer illness duration and higher scores on all PANSS subscales were associated with lower MoCA scores, whereas longer education and older age at diagnosis were positively correlated with cognitive performance. Although prior research has suggested dose-related cognitive impairment, our findings did not provide evidence supporting this association in young, well-characterised patients within the constraints of a cross-sectional observational design. These results indicate that effective therapeutic dosing can be pursued with appropriate clinical monitoring, while acknowledging that potential cognitive effects should still be taken into consideration. Cognitive deficits are present from an early age of schizophrenia. Cognitive scores are not significantly associated with antipsychotic dose. Higher psychotic symptoms are linked to lower cognitive scores. A longer illness duration is associated with poorer cognitive function. A homogeneous and clinically stable sample reduces clinical heterogeneity and improves comparability across participants.