Why does genetic causal information alter perceived treatment effectiveness? An analogue study

Objectives. When a health problem is perceived as having a genetic cause, this appears to increase the perceived effectiveness of pharmacological treatments and reduce perceived effectiveness of non-pharmacological treatments. Potential mediators of this effect include causal attributions, perceived severity, and perceived control over the health problem. This study aimed to use experimental methods to establish which beliefs mediate the effect of genetic causal information on perceived effectiveness of treatments.Design. A 4(cause: environmental, family history, genetic test, family history & genetic test) x2(severity: higher or low) between- subjects design using vignettes about heart disease risk, obesity or depression.

Methods. A total of 647 adults, randomly assigned to read one of the experimental vignettes, were interviewed. Key outcomes were perceived effectiveness of medication and of non- pharmacological treatments. Potential mediators of perceived severity, perceived controllability, and causal attributions were also assessed.

Results. For heart disease risk, genetic causes reduced perceived effectiveness of nonpharmacological treatments (an effect mediated by causal attributions and perceived control) but did not influence perceived medication effectiveness. For obesity, neither severity nor cause influenced the perceived effectiveness of either treatment. For depression, genetic causes only increased perceived effectiveness of medication for more severe depression, an effect mediated by perceived control.

Conclusions. The impact of genetic causal information on perceived effectiveness of treatments varies with type of health problem. When genetic causal information influences perceived treatment effectiveness, it does so by altering causal attributions and perceived controllability. However, these effects are small and unlikely to translate into clinically meaningful differences in health-enhancing behaviours.