Causal and Associational Language in Observational Health Research: A Systematic Evaluation

We estimated the degree to which language used in the high-profile medical/public health/epidemiology literature implied causality using language linking exposures to outcomes and action recommendations; examined disconnects between language and recommendations; identified the most common linking phrases; and estimated how strongly linking phrases imply causality. We searched for and screened 1,170 articles from 18 high-profile journals (65 per journal) published from 2010-2019. Based on written framing and systematic guidance, 3 reviewers rated the degree of causality implied in abstracts and full text for exposure/outcome linking language and action recommendations. Reviewers rated the causal implication of exposure/outcome linking language as none (no causal implication) in 13.8%, weak in 34.2%, moderate in 33.2%, and strong in 18.7% of abstracts. The implied causality of action recommendations was higher than the implied causality of linking sentences for 44.5% or commensurate for 40.3% of articles. The most common linking word in abstracts was associate (45.7%). Reviewers' ratings of linking word roots were highly heterogeneous; over half of reviewers rated association as having at least some causal implication. This research undercuts the assumption that avoiding causal words leads to clarity of interpretation in medical research.

Automated summary

The research examined the implication of causality in language used in high-profile medical literature, revealing varying degrees of causal implication in exposure/outcome linking language in abstracts and full texts, as well as a higher implication of causality in action recommendations compared to linking sentences.