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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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Related in: MedlinePlus

A single episode of illness and demonstration only during illness.The cultural fitness (a–c) and probability of spread (d–f) of self-medicative treatments, plotted as a function of treatment efficacy, , when there is a single episode of illness and demonstration occurs only during illness. Left (a and d), effect of varying maximum rate of abandonment, . Middle (b and e), effect of varying rate of recovery, . Right (c and f), effect of varying rate of decay in treatment abandonment. Unless otherwise stated , , , , , , ,  and  (see also Methods and Table 1).
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pone-0005192-g003: A single episode of illness and demonstration only during illness.The cultural fitness (a–c) and probability of spread (d–f) of self-medicative treatments, plotted as a function of treatment efficacy, , when there is a single episode of illness and demonstration occurs only during illness. Left (a and d), effect of varying maximum rate of abandonment, . Middle (b and e), effect of varying rate of recovery, . Right (c and f), effect of varying rate of decay in treatment abandonment. Unless otherwise stated , , , , , , , and (see also Methods and Table 1).

Mentions: First consider cases with a single bout of illness and treatment demonstration restricted to sick individuals (Equation (2), Figure 3). Across a broad range of conditions, the most efficacious treatments are not necessarily those most likely to spread, and superstitious treatments with no efficacy (), or even maladaptive practices (), frequently have the highest cultural fitness (). Superstitious treatments and maladaptive practices can spread because their very ineffectiveness results in sick individuals demonstrating the practice for longer than efficacious treatments, leading to more salient demonstration and more converts. This outcome occurs in spite of the fact that we assume that the less effective the treatment, the more likely a sick individual will abandon it, resulting in n-shaped functions for cultural fitness (Figure 3a–c) and probability of spread of the treatment (Figure 3d–f) The observed relationships represent a trade-off between duration of illness which is associated with demonstration of the treatment on one hand and retention of the treatment due to its efficacy on the other hand. That is, persistent illness leads to prolongued demonstration of the practice, yet an increased rate of abandonment of an ineffective treatment. In contrast, increased retention of an effective treatment is also associated with reduced demonstration of the practice.


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

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

A single episode of illness and demonstration only during illness.The cultural fitness (a–c) and probability of spread (d–f) of self-medicative treatments, plotted as a function of treatment efficacy, , when there is a single episode of illness and demonstration occurs only during illness. Left (a and d), effect of varying maximum rate of abandonment, . Middle (b and e), effect of varying rate of recovery, . Right (c and f), effect of varying rate of decay in treatment abandonment. Unless otherwise stated , , , , , , ,  and  (see also Methods and Table 1).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0005192-g003: A single episode of illness and demonstration only during illness.The cultural fitness (a–c) and probability of spread (d–f) of self-medicative treatments, plotted as a function of treatment efficacy, , when there is a single episode of illness and demonstration occurs only during illness. Left (a and d), effect of varying maximum rate of abandonment, . Middle (b and e), effect of varying rate of recovery, . Right (c and f), effect of varying rate of decay in treatment abandonment. Unless otherwise stated , , , , , , , and (see also Methods and Table 1).
Mentions: First consider cases with a single bout of illness and treatment demonstration restricted to sick individuals (Equation (2), Figure 3). Across a broad range of conditions, the most efficacious treatments are not necessarily those most likely to spread, and superstitious treatments with no efficacy (), or even maladaptive practices (), frequently have the highest cultural fitness (). Superstitious treatments and maladaptive practices can spread because their very ineffectiveness results in sick individuals demonstrating the practice for longer than efficacious treatments, leading to more salient demonstration and more converts. This outcome occurs in spite of the fact that we assume that the less effective the treatment, the more likely a sick individual will abandon it, resulting in n-shaped functions for cultural fitness (Figure 3a–c) and probability of spread of the treatment (Figure 3d–f) The observed relationships represent a trade-off between duration of illness which is associated with demonstration of the treatment on one hand and retention of the treatment due to its efficacy on the other hand. That is, persistent illness leads to prolongued demonstration of the practice, yet an increased rate of abandonment of an ineffective treatment. In contrast, increased retention of an effective treatment is also associated with reduced demonstration of the practice.

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
Related in: MedlinePlus