Meta-Analysis

What is Meta-Analysis?

Meta-Analysis is a precise quantitative integration and statistical analysis of effect sizes
It focuses on quantitative data, combining the results of multiple studies
It is used to provide estimates of effects and resolve inconsistencies amongst study results

Details

Meta-Analysis

Meta-Analysis is a specific type of evidence synthesis that focuses on quantitatively combining the results of multiple studies using statistical methods. It is used to provide precise estimates of effects and to resolve inconsistencies among study results by pooling quantitative data.

Purpose:

To Quantitatively Combine Results: The primary aim is to statistically combine results from multiple quantitative studies to provide a more precise estimate of effect or association.
To Increase Statistical Power: To enhance the statistical power and generalisability of findings by pooling data from several studies.
To Resolve Uncertainty: To address inconsistencies or discrepancies in the results of individual studies by providing a consolidated estimate.

Characteristics:

Quantitative Focus: Focuses specifically on quantitative data and uses statistical methods to integrate results from multiple studies.
Statistical Analysis: Involves the use of statistical techniques to calculate pooled effect sizes, such as odds ratios, mean differences, or risk ratios.
Homogeneity Assessment: Assesses the degree of heterogeneity between studies, which refers to variations in study results. Techniques like I² statistics are used to measure this.
Data Extraction: Involves detailed extraction of quantitative data from studies, including sample sizes, effect sizes, and measures of variance.
Model Selection: Uses different statistical models (e.g., fixed-effect or random-effects models) to combine study results, depending on the level of heterogeneity and the research question.
Meta-Analytic Techniques: Employs various meta-analytic techniques, including subgroup analysis, sensitivity analysis, and publication bias assessment, to ensure robustness and reliability of the findings.
Forest Plots: Often presents results using forest plots, which visually display the effect sizes and confidence intervals of individual studies and the overall pooled estimate.

Timescale:

6-18 months, usually part of a systematic review.

Example

Example: Meta-Analysis on Psychological Interventions for PTSD

This meta-analysis combined data from multiple studies to evaluate the effectiveness of different types of psychological therapies for PTSD.

Title: A multidimensional meta-analysis of psychotherapy for PTSD

Authors: R. Bradley, J. Greene, E. Russ, L. Dutra, and D. Westen

Published In: American Journal of Psychiatry, 2005

Purpose: The primary aim of this meta-analysis was to evaluate the efficacy of various psychological interventions for the treatment of post-traumatic stress disorder (PTSD). The study sought to determine which types of psychotherapy were most effective in reducing PTSD symptoms.

Key Characteristics of the Meta-Analysis:

Comprehensive Literature Search: The researchers conducted an extensive search of multiple databases to identify relevant randomised controlled trials (RCTs) and controlled clinical trials (CCTs) that evaluated psychological treatments for PTSD.
Inclusion and Exclusion Criteria: Clear criteria were established for including studies in the meta-analysis. Only studies that provided data on PTSD symptom outcomes and employed a control group were included.
Quality Assessment: The included studies were assessed for methodological quality, and only high-quality studies were included in the final analysis. This ensured the reliability and validity of the meta-analysis findings.
Data Extraction and Coding: Data on study characteristics, treatment types, and PTSD outcomes were systematically extracted and coded. This included details such as sample size, type of intervention, duration of treatment, and outcome measures.
Statistical Analysis: The meta-analysis used statistical techniques to combine the results of individual studies. This involved calculating effect sizes for each study and using random-effects models to account for variability between studies.

Key Findings:

The meta-analysis found that psychological interventions, particularly cognitive-behavioural therapy (CBT), were effective in reducing PTSD symptoms.
CBT showed the largest effect sizes, indicating it was the most effective treatment compared to other psychological interventions.
Other effective treatments included eye movement desensitisation and reprocessing (EMDR) and stress inoculation training (SIT), although their effect sizes were smaller than those for CBT.
The findings supported the use of psychological therapies as a first-line treatment for PTSD, with CBT being the most recommended approach.

Impact:

This meta-analysis provided robust evidence supporting the efficacy of psychological interventions, especially CBT, for treating PTSD. It has influenced clinical guidelines and practice, promoting the use of evidence-based psychological therapies for individuals with PTSD. The study has been widely cited and used as a reference for developing treatment protocols and informing clinical decision-making.

Summary:

This meta-analysis by Bradley et al. is a prime example of how meta-analytic techniques can be used to synthesise data from multiple studies and provide evidence on the effectiveness of different treatments. By combining data from numerous high-quality studies, the meta-analysis offered clear and reliable conclusions about the efficacy of psychological interventions for PTSD. This study has had a significant impact on the field of mental health, guiding treatment recommendations and improving outcomes for individuals with PTSD.

NIHR Example:

Recent Meta analysis (from NIHR Journals library database 30/7/2024)

A systematic review with mixed treatment comparisons meta analysis of anti-depressant treatment for adults with chronic pain

Funding: NIHR Health Technology Assessment Programme, 2024 https://www.fundingawards.nihr.ac.uk/award/NIHR128782

Video Resources

"A Three Minute Primer on Meta-Analysis" As the title suggests, this video gives a brief, yet informative, introduction to what meta-analysis is; ideal for viewers looking for a quick understanding. (TARG Bristol 3:02 minutes)
What is meta analysis? Dr Tim Barker, explains what a meta-analysis is, why we should perform a meta-analysis, and how the results of a meta-analysis can assist systematic reviewers to answer a question regarding the effectiveness of an intervention. (Joanna Briggs Institute 3:56 minutes)