Methodological differences in measuring post-traumatic stress disorder: a systematic review of the global literature during the Covid-19 pandemic

Introduction

The Covid-19 pandemic spurred an unprecedented rise in mental health research globally, with posttraumatic stress disorder (PTSD) emerging as a prominent concern. However, estimates of PTSD prevalence during the pandemic varied widely, raising questions about methodological consistency in how PTSD was measured and conceptualized during the pandemic. We systematically reviewed the global literature assessing PTSD prevalence during the Covid-19 pandemic, with a focus on methodological differences in measurement, population sampling, and application of screening and diagnostic criteria.

Methods

Following PRISMA guidelines, we searched six databases for peer-reviewed, English-language articles published between January 1, 2020, and July 12, 2024. Eligible studies assessed PTSD prevalence in general adult populations and explicitly linked PTSD assessment to the Covid-19 pandemic. We extracted data on study design, sampling strategy, PTSD measurement instruments, prevalence estimates, and whether included studies employed Criterion A in PTSD screening/diagnosis. Studies focusing exclusively on subpopulations (e.g., healthcare workers) were excluded.

Results

A total of 147 articles met inclusion criteria, with significant representation from Italy, China, and the United States. Eligible studies included 11 unique PTSD screening instruments with multiple cut-off scores. The most commonly used screening instruments were the PTSD Checklist (PCL; 41.5 %) and the Impact of Event Scale (IES; 29.9 %). PTSD prevalence estimates varied within and across countries and screening instruments. Use of Criterion A varied widely: 42.9 % of studies designated Covid-19 as the traumatic event, 44.9 % removed the Criterion A requirement, and 12.2 % required a non-pandemic qualifying trauma. Only 17 % of studies used representative sampling methods, and just 13 were longitudinal or serial cross-sectional. Among representative studies, PTSD prevalence still varied widely, from 1.2 % in China to 44.9 % in Italy.

Conclusions

This review reveals substantial methodological heterogeneity in PTSD prevalence assessments during the Covid-19 pandemic. Inconsistent use of diagnostic criteria, varied screening instruments and cutoffs, limited longitudinal data, and geographical bias all constrain cross-study comparability. Despite these challenges, most studies reported PTSD prevalence above pre-pandemic global estimates, supporting the classification of the Covid-19 pandemic as a mass traumatic event. Future global mental health surveillance efforts should prioritize standardized PTSD assessment, representative sampling, and longitudinal designs to better capture trends in the population mental health impacts of large-scale mass traumatic events.