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Beliefs, critical thinking and evidence-based medicine
  1. Haris Achilleos
  1. Correspondence to Dr Haris Achilleos, Department of Paediatrics, St Mary’s Hospital, Imperial College Healthcare NHS Trust, London W2 1NY, UK; haris.achilleos{at}

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The field of evidence-based medicine (EBM) has evolved tremendously since the term was coined 25 years ago. There are improved tools for use in daily practice, helping clinicians and patients make informed decisions about treatment choices. The recently published ‘Evidence based medicine manifesto for better healthcare’,1 devised by the BMJ and the University of Oxford’s Centre for Evidence Based Medicine, has been read with great interest. Nonetheless, one can’t help but wonder: even when using the most up-to-date resources, how informed and unbiased are our clinical decisions, when we are subconsciously governed by our underlying beliefs, shaped by past experiences?

As humans, we carry perceptions that affect our daily decisions and actions. Studies in cognitive sciences have shown that our subconscious mind is constantly seeking evidence to support our pre-existing ideas, while any information challenging these notions is approached with psychological discomfort, scepticism and an unconscious drive to refute them (as part of the phenomenon of ‘cognitive dissonance’).2 3

Clinicians are not immune to the impact personal beliefs have on their daily clinical judgements and decision making. We daily form opinions about what treatment works for which patient population; we create mental systems for reaching diagnoses and shape our views on how diseases behave. We form and adopt heuristics around our clinical judgements and decision making although heuristics often lead to misjudgement and error.4 We often witness different practices for common clinical presentations between different departments, or even among different clinicians within the same department. Most senior doctors would support their choice of practice as a result of years of experience and observation. In all but very rare occasions, doctors’ preferences stem out of a genuine desire to provide the best possible treatment to their patients. Yet, even when we feel confident that we have reached the most appropriate, most informed and evidence-guided decision, practices vary. Daniel Kahneman, expert in the psychology of judgement and decision making, argues that the degree of subjective confidence does not directly correlate with accuracy.4

However, the oft-quoted practice of cherry-picking has, once again, become a topical subject, as it has been at the core of the recent ‘Hunt-Hawking debate’.5 Undoubtedly, cherry-picking can lead to biased conclusions and manipulation of evidence and subsequently unsafe practices. Nonetheless, in a more benign form, cherry-picking is rather common in daily practice. It could be argued that many ethically and scientifically trained, well-meaning clinicians are being unconsciously selective while sieving between evidence and anecdote when seeking answers to a topic of interest. We daily fall into practices directed by our subconscious cognitive biases.

Evidence-based decision making is seen as a means of achieving standardisation of treatment practices, safety and clinical efficiency. Critical appraisal skills are taught using a number of traditional tools, such as checklists, while employing basic statistical concepts for interpretation of published studies. However, historical research has shown that when given evidence to appraise, people are more likely to identify study flaws and biases when the findings do not match their preconceived opinions than if they do.6 7 These interpretations are probably taking place at a subconscious level, while the ‘appraisers’ continue to believe that they have practised a genuinely critical review of the evidence, in an unbiased and systematic manner. As Ben Goldacre summarises, ‘our assessment of the quality of new evidence is biased by our previous beliefs’.8

It appears that we often teach and talk about EBM skills, overlooking a more basic science: that of critical thinking. Critical thinking comprises a set of skills necessary for daily reasoning and academic analytical thinking.9 These are the skills used in the conscious formation of arguments and syllogisms and their evaluations in a dialogue. In this context, critical thinking and EBM could be approached from an epistemological viewpoint. It can be argued that being taught these disciplines early on in their academic and professional lives could help young graduates discern logic from fallacy. This could act as a stepping stone for the future generation of healthcare professionals to develop their critical appraisal skills and practise in an unbiased, evidence-based manner. In other words, we need to start teaching students and young healthcare professionals the value of challenging, deconstructing and reconstructing their own belief systems and those of others, bringing awareness to the subconscious mechanisms that create and sustain them.


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  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.