Bayesian Meta-analysis of Multiple Continuous Treatments with Individual Participant-Level Data: An Application to Antipsychotic Drugs

Meta-analysis of Total Effect Decomposition in the Presence of Multiple Mediators: The Example of Schizophrenia Treatment

BACKGROUND

Causal mediation analysis addresses mechanistic questions by decomposing and quantifying effects operating through different pathways. Because most individual studies are underpowered to detect mediating effects, we outlined a parametric approach to meta-analyzing causal mediation and interaction analyses with multiple mediators, compared it with a bootstrap-based alternative, and discussed its limitations.

METHODS

We employed fixed- and random-effects multivariate meta-analyses to integrate evidence on treatment-mediators and mediators-outcome associations across trials. We estimated path-specific effects as functions of meta-analyzed regression coefficients; we obtained standard errors using the delta method. We evaluated the performance of this approach in simulations and applied it to assess the mediating roles of positive symptoms of schizophrenia and weight gain in the treatment effect of paliperidone ER on negative symptoms across four efficacy trials.

RESULTS

Both simulations and the application showed that the meta-analytic approaches increased statistical power. In the application, we observed substantial mediating effects of positive symptoms (proportions mediated from fixed-effects meta-analysis: (Equation is included in full-text article.)). Weight gain may have beneficial mediating effects; however, such benefit may disappear at high doses when metabolic side effects were excessive.

CONCLUSIONS

Meta-analyzing causal mediation analysis combines evidence from multiple sources and improves power. Targeting positive symptoms may be an effective way to reduce negative symptoms that are challenging to treat. Future work should focus on extending the existing methods to allow for more flexible modeling of mediation.

Dose-dependent effects of antipsychotics on efficacy and adverse effects in schizophrenia

BACKGROUND

Antipsychotics are a cornerstone of pharmacological treatment of schizophrenia. Improved understanding of the dose-response relationship of antipsychotics in terms of efficacy, adverse effects, and mortality can help to optimize the pharmacological treatment of schizophrenia.

METHODS

This narrative literature review summarizes current evidence on the relationship of antipsychotic dose with efficacy, adverse effects, and mortality in patients with schizophrenia.

RESULTS

The efficacy of antipsychotics generally appeared to be highly dose-dependent in the acute phase of schizophrenia, with each antipsychotic having a specific dose-response curve. The presence or absence of dose-dependency and its extent varied according to the type of adverse effect. Parkinsonism, hyperprolactinemia, weight gain, and neurocognitive impairment appeared to be dose-related. The following adverse effects might be at least somewhat dose-dependent: akathisia, tardive dyskinesia, osteoporosis, sexual dysfunction, diabetes mellitus, myocardial infarction, stroke, thromboembolism, QT interval prolongation, anticholinergic adverse effects, somnolence, pneumonia, hip fracture, and neuroleptic malignant syndrome. In contrast, the relationships of antipsychotic dose with dyslipidemia, hypotension, seizure, sialorrhea, and neutropenia and agranulocytosis remained unclear due to mixed findings and/or limited data. Although a higher lifetime cumulative antipsychotic dose might contribute to higher mortality, it is still difficult to conclude whether mortality increases in a dose-dependent manner.

CONCLUSION

These findings could help clinicians to optimize antipsychotic treatment in patients with schizophrenia by balancing risks and benefits in clinical practice. However, further investigations with larger sample sizes and more robust study designs that focus on each antipsychotic agent are needed.