differential patterns of blood oxygenation in the prefrontal cortex between patients with methamphetamineinduced psychosis and schizophrenia despite some slight differences in symptomatology differential diagnosis of methamphetamineinduced psychosis map versus schizophrenia can be challenging because both disorders present a large overlap in their clinical symptoms however a recent study has shown that nearinfrared spectroscopy nirs performed during a cognitive task can be a powerful tool to differentiate between these two disorders here we evaluated verbal fluency task performance during nirs in 15 patients diagnosed with map and 19 with schizophrenia matched for age and sex we used prefrontal probes and a 24channel nirs machine to measure the relative concentrations of oxyhaemoglobin every 01s during the task for each patient the neurocognitive function and clinical psychopathology were evaluated using the positive and negative symptom scale panss and the brief assessment of cognition in schizophrenia bacs oxyhaemoglobin changes in the prefrontal cortex were significantly higher in the map group compared to those in the schizophrenia group particularly in the right dorsolateral prefrontal cortex in contrast we found no significant difference in panss and bacs scores our findings suggest that nirs measurement could be applied to differentiate patients with map from those with schizophrenia even in cases where clinical symptoms are similar