One reason is that physicians may value their own experiences (i.e., learning by doing) over the accumulated experience across many providers. A paper by Berndt et al. (2015) look at physician prescribing patterns of antipsychotic. They note that some physicians concentrate in prescribing specific antipsychotics and others concentrate on prescribing other ones.
The authors claim the reason for this is that the physicians learn-by-doing. For instance, it is more difficult for a physician to learn how to adequately titrate the dose of 10 antipsychotics compared to focusing on how best to do this for a single one. This approach is clearly sensible in many cases, but it limits the spread of evidence-based guidelines.
…advances in the practice of evidence-based medicine are likely to be constrained considerably if physicians limit the evolution of their evidentiary platform to their own learning-by-doing experiences, down-weighting accumulating evidence reported by other prescribers. Concentrated,“one size fits all” prescribing behavior could fail to exploit opportunities to successfully tailor or “personalize” medical treatments to patients’ idiosyncratic genetic, environmental and behavioral characteristics.
The authors found that psychiatrists who prescribe a high-volume of antipsychotics are the ones most likely to deviate from national market shares.
Another explanation for their results is pharmaceutical detailing. Pharmaceutical firms marketing choice could explain physician decisions to specialize in prescribing specific drugs. However, the authors find that:
…the highest volume psychiatrists in the youngest quartile prescribe a larger share of old drugs. This is consistent with our learning-by-doing framework, but is at odds with the detailing hypothesis, because these youngest high-volume psychiatrists are likely to have been heavily detailed on new drugs, but are likely never to have been detailed on the old drugs.
- Ernst R. Berndt, Robert S. Gibbons, Anton Kolotilin, Anna Levine Taub, The heterogeneity of concentrated prescribing behavior: Theory and evidence from antipsychotics, Journal of Health Economics, Volume 40, March 2015, Pages 26-39, ISSN 0167-6296, http://dx.doi.org/10.1016/j.jhealeco.2014.11.003.