The auditory P200 is both increased and reduced in schizophrenia?: a meta-analytic dissociation of the effect for standard and target stimuli in the oddball task

Objective: Conflicting reports of P200 amplitude and latency in schizophrenia have suggested that this component is increased, reduced or does not differ from healthy subjects. A systematic review and meta-analysis were undertaken to accurately describe P200 deficits in auditory oddball tasks in schizophrenia. Methods: A systematic search identified 20 studies which were meta-analyzed. Effect size (ES) estimates were obtained: P200 amplitude and latency for target and standard tones at midline electrodes. Results: The ES obtained for amplitude (Cz) for standard and target stimuli indicate significant effects in opposite directions: standard stimuli elicit smaller P200 in patients (d = -0.36; 95% CI [-0.26, -0.08]); target stimuli elicit larger P200 in patients (d = 0.48; 95% CI [0.16, 0.82]). A similar effect occurs for latency at Cz, which is shorter for standards (d = -0.32; 95% CI [-0.54, -0.10]) and longer for targets (d = 0.42; 95% CI [0.23, 0.62]). Meta-regression analyses revealed that samples with more males show larger ES for amplitude of target stimuli, while the amount of medication was negatively associated with the ES for the latency of standards. Conclusions: The results obtained suggest that claims of reduced or augmented P200 in schizophrenia based on the sole examination of standard or target stimuli fail to consider the stimulus effect. Significance: Quantification of effects for standard and target stimuli is a required first step to understand the nature of P200 deficits in schizophrenia