Intended for healthcare professionals

Letters Covid-19’s known unknowns

Covid-19’s known unknowns: population shared decision making

BMJ 2020; 371 doi: (Published 23 November 2020) Cite this as: BMJ 2020;371:m4514
  1. Mark Cobain, director
  1. Younger Lives, London SE1 4YR, UK
  1. mark{at}

I agree with Davey Smith and colleagues about the expression of certainty in covid-19 communications and the effects on trust and public beliefs.1

Certainty is reassuring for the general population at times of crisis. Certainty around severity increases perceived susceptibility, and clarity on resulting required behaviours provides a sense of control. But with declining certainty, we erode that trust. This is diametrically opposed to our clinical model of shared decision making, which helps patients weigh up the pros and cons of difficult health trade-offs so that decisions are made through discussion of values, preferences, and different likely outcomes.

Current communication around covid-19 has led to polarisation and dismissal of rival positions. The evidence base usually acts as an impartial referee in shared decision making, but, as the authors rightly point out, the evidence is uncertain for a disease in its infancy. The presentation of personally changed positions is a fitting end to the article.

Uncertainty is often not deemed fit for public consumption. We recognise that clinical decision making can be surrounded by uncertainty, so we discuss this with patients using a combination of their preferences and agreed further investigations. Interestingly, as new evidence on the condition comes to light, we may both change our initial positions together, and this might be a worthy temperament in public communication. We should be much better at representing and visualising the pros and cons of different positions, with more debate on the consequences of one route or another.

The negative effects of covid-19 on population mental health are in part due to ongoing economic and social factors and bereavement. But loss of trust in science could have even greater effects in the long term. The short term focus on communications for immediate behaviour change will not improve that.


  • Competing interests: I am a director of an organisation that focuses on health communication strategies.

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