We understand that social policies have great potential to affect health, but studies that aim to document the associations between policy interventions and health outcomes are often methodologically weak. Association studies are unable to identify the directionality of causal pathways (e.g., do chronically ill people make less money because they are able to work less or does low income exacerbate illness, or both?), let alone draw definitive conclusions about the effects of social policies on health.

On such weak data, investments in “social determinants of health” are often made. So a recent study that systematically reviews and meta analyzes the effects of social experiments on health is particularly welcome. Authors Courtin et al. published a that review in Milbank Quarterly, based on 38 randomized trials investigating the relationships between social policies and health. They found that interventions in early life, income, and health insurance have the potential to improve health, yet most of the studies included in the review were not powered to detect health effects and had a significant risk of bias.

The authors concluded that the hypothesis that “social policy is health policy” was broadly supported. Experiments which positively affected their target socioeconomic group were more likely to report positive health effects. Other conclusions include:

  • Based on the strength of the evidence conducted to date, over 75% of the studies reviewed (not all of which were published in peer-reviewed journals) were underpowered to detect a health effect. However, among the studies that were sufficiently powered to detect a health effect, about half (49%) found improvements. Of the remaining half, 44% showed a null effect and 7% were linked to negative health outcomes.
  • Most of the early life and education interventions caused positive health effects for a broad range of health outcomes, and when Courtin et al. conducted a meta-analysis, they found that these social programs were associated with an 8% decrease in smoking prevalence, a small but significant reduction, given that smoking is strongly associated with other negative health outcomes and risk-taking behavior.
  • Among individual studies, income support and health insurance programs caused the greatest increase in population health. However, when looking across all studies, Courtin et al.’s meta-analysis did not demonstrate consistent benefits.
  • A small proportion of the studies demonstrated harmful effects of social policies on health, though these were primarily among welfare-to-work interventions, programs designed to promote self-sufficiency, through which recipients must perform work activities to receive cash aid.
  • Strong publication bias was present among the reviewed studies, where significant findings and positive health effects of social policies were more likely to be published in a peer-reviewed journal.

Read the whole study here.