Limits...
From traditional medicine to witchcraft: why medical treatments are not always efficacious.

Tanaka MM, Kendal JR, Laland KN - PLoS ONE (2009)

Bottom Line: With serious doubts about the efficacy and safety of many treatments, the industry remains steeped in controversy.Low-efficacy practices sometimes spread because their very ineffectiveness results in longer, more salient demonstration and a larger number of converts, which more than compensates for greater rates of abandonment.These models also illuminate a broader range of phenomena, including the spread of innovations, medical treatment of animals, foraging behaviour, and self-medication in non-human primates.

View Article: PubMed Central - PubMed

Affiliation: Evolution & Ecology Research Centre, School of Biotechnology & Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia. m.tanaka@unsw.edu.au

ABSTRACT
Complementary medicines, traditional remedies and home cures for medical ailments are used extensively world-wide, representing more than US$60 billion sales in the global market. With serious doubts about the efficacy and safety of many treatments, the industry remains steeped in controversy. Little is known about factors affecting the prevalence of efficacious and non-efficacious self-medicative treatments. Here we develop mathematical models which reveal that the most efficacious treatments are not necessarily those most likely to spread. Indeed, purely superstitious remedies, or even maladaptive practices, spread more readily than efficacious treatments under specified circumstances. Low-efficacy practices sometimes spread because their very ineffectiveness results in longer, more salient demonstration and a larger number of converts, which more than compensates for greater rates of abandonment. These models also illuminate a broader range of phenomena, including the spread of innovations, medical treatment of animals, foraging behaviour, and self-medication in non-human primates.

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The relationship between rate of abandonment and efficacy.Here we show several curves by varying the parameter  and setting  and  (see Methods for interpretation of parameter values).
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pone-0005192-g002: The relationship between rate of abandonment and efficacy.Here we show several curves by varying the parameter and setting and (see Methods for interpretation of parameter values).

Mentions: Further assume that an individual who adopts the trait may abandon it or revert to a previous practice. The rate of abandonment is a decreasing function of the rate of recovery from the disease. This response is based on the assumption that sick individuals will become increasingly dissatisfied with their treatment as the time to recovery increases, and will abandon treatments that are perceived to be ineffective. Let this function be(1)where is the maximum rate of abandonment, occurring when the trait is completely maladaptive (), and determines how strongly recovery influences abandonment (see Figure 2). While is a function of four parameters, we will write it simply as for convenience. Although we set this function to be an exponential decay, exploration of alternative forms of the relationship between abandonment and efficacy (e.g. hyperbolic function) showed they do not influence the qualitative outcomes of the analysis.


From traditional medicine to witchcraft: why medical treatments are not always efficacious.

Tanaka MM, Kendal JR, Laland KN - PLoS ONE (2009)

The relationship between rate of abandonment and efficacy.Here we show several curves by varying the parameter  and setting  and  (see Methods for interpretation of parameter values).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2664922&req=5

pone-0005192-g002: The relationship between rate of abandonment and efficacy.Here we show several curves by varying the parameter and setting and (see Methods for interpretation of parameter values).
Mentions: Further assume that an individual who adopts the trait may abandon it or revert to a previous practice. The rate of abandonment is a decreasing function of the rate of recovery from the disease. This response is based on the assumption that sick individuals will become increasingly dissatisfied with their treatment as the time to recovery increases, and will abandon treatments that are perceived to be ineffective. Let this function be(1)where is the maximum rate of abandonment, occurring when the trait is completely maladaptive (), and determines how strongly recovery influences abandonment (see Figure 2). While is a function of four parameters, we will write it simply as for convenience. Although we set this function to be an exponential decay, exploration of alternative forms of the relationship between abandonment and efficacy (e.g. hyperbolic function) showed they do not influence the qualitative outcomes of the analysis.

Bottom Line: With serious doubts about the efficacy and safety of many treatments, the industry remains steeped in controversy.Low-efficacy practices sometimes spread because their very ineffectiveness results in longer, more salient demonstration and a larger number of converts, which more than compensates for greater rates of abandonment.These models also illuminate a broader range of phenomena, including the spread of innovations, medical treatment of animals, foraging behaviour, and self-medication in non-human primates.

View Article: PubMed Central - PubMed

Affiliation: Evolution & Ecology Research Centre, School of Biotechnology & Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia. m.tanaka@unsw.edu.au

ABSTRACT
Complementary medicines, traditional remedies and home cures for medical ailments are used extensively world-wide, representing more than US$60 billion sales in the global market. With serious doubts about the efficacy and safety of many treatments, the industry remains steeped in controversy. Little is known about factors affecting the prevalence of efficacious and non-efficacious self-medicative treatments. Here we develop mathematical models which reveal that the most efficacious treatments are not necessarily those most likely to spread. Indeed, purely superstitious remedies, or even maladaptive practices, spread more readily than efficacious treatments under specified circumstances. Low-efficacy practices sometimes spread because their very ineffectiveness results in longer, more salient demonstration and a larger number of converts, which more than compensates for greater rates of abandonment. These models also illuminate a broader range of phenomena, including the spread of innovations, medical treatment of animals, foraging behaviour, and self-medication in non-human primates.

Show MeSH