Meta-analysis of studies in China about changes in P300 latency and amplitude that occur in patients with schizophrenia during treatment with antipsychotic medication

BACKGROUND: Studies using event-related potential (ERP) methods have reported a relationship between the cognitive dysfunction of patients with schizophrenia and P300 latency and amplitude, but it remains uncertain whether or not these indices change as cognitive functioning improves with pharmacological treatment. AIM: Pool the results from follow-up studies conducted in China to determine the relationship of treatment with antipsychotic medication to changes in P300 indices. METHODS: Studies conducted in China and published in English or Chinese from January 1982 to December 2011 that reported P300 latency and amplitude in patients with schizophrenia before and after treatment with antipsychotic medications were identified by electronic and hand searches, and the 12 studies that met inclusion criteria for the meta-analysis were independently reviewed by two evaluators. The peak P300 amplitude results for the 17 samples reported in the 12 studies were homogenous so a fixed-effects model was used to assess pooled standardized effect size (PSES); but the results for P300 latency were heterogeneous so a random-effects model was used to compute PSES. Publication bias was assessed using Egger's test, Begg's test and funnel plots. RESULTS: Of the pooled sample of 611 participants, the 502 participants (82.2%) who completed P300 latency and amplitude measures both before and after treatment were included in the meta-analysis. We found that antipsychotic treatment is associated with a small but significant increase in the amplitude of P300 (PSES=0.39, 95% CI [0.26, 0.51], z=6.14, p<0.001) and a small but significant decrease in the latency of P300 (PSES= -0.29, 95% CI [-0.51, -0.07]; z=2.58; p=0.010). There was no significant publication bias in either of the results. CONCLUSION: In contrast to meta-analysis from western countries — that are primarily based on cross-sectional studies — the current meta-analysis of follow-up treatment studies of schizophrenia in China found that P300 amplitude and latency both change with pharmacological treatment. These findings suggest that P300 indices, particularly P300 amplitude, could be valuable biomarkers to monitor changes in cognitive functioning during treatment of patients with schizophrenia.