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The Use of Evidence in Clinical Reasoning


The professional context in which clinical psychologists and psychotherapists work is characterized by uniqueness, uncertainty and value-conflicts. Given this context, what kind of evidence can they use to orient their interventions in a reasonable and purposeful way? In this paper, the author addresses the question of the epistemological underpinning of clinical reasoning. On the basis of current concepts in philosophy of science, a distinction is made between statistical thinking and thinking in cases as two epistemic approaches relevant to the field of clinical psychology and psychotherapy. Each of these thinking styles is a unique mode of investigating, conceptualizing and interacting with objects of interest. The author argues that statistical thinking and evidence in terms of probabilistic knowledge are epistemically less suited to support clinical reasoning and decision-making in practicing psychologists and therapists. Thinking in cases relies on evidence from within the case and evidence from clinical experience. This epistemic mode permits the practitioner to address unique situations by understanding the case from within and in reference to other cases, and to address uncertainty by intervening in causal processes that are at work at the level of the case. Thinking in cases is epistemically more coherent with the context in which clinicians work. In the conclusion, suggestions are made for bridging the gap between science and practice.

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This study did not involve the collection of data from human or animal subjects.


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I would like to thank professor Emmanuelle Zech, Hubert de Condé and Niccolò Polipo for their feedback on an earlier version of this manuscript.


The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

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Conceptualization, investigation, writing (original draft, review and editing) by JW. The author read and approved the final manuscript.

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Correspondence to Jochem Willemsen.

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The author has no relevant financial or non-financial interest to disclose.

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This study did not involve the collection of data from human or animal subjects.

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Willemsen, J. The Use of Evidence in Clinical Reasoning. J Contemp Psychother (2022).

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  • Clinical reasoning
  • Evidence-based practice
  • Epistemology
  • Thinking in cases
  • Science-practice gap