A study on direct-to-consumer (DTC) drug advertising published Monday in Nature Human Behavior finds that consumers perceive drugs to be less risky when ads for the drug list all of its side effects compared to when only serious side effects are listed.
"When commercials list severe side effects along with those that are most frequent…it dilutes consumers' judgements of the overall severity of the side effects," write authors Niro Sivanathan, associate professor of organizational behavior at the London Business School, and PhD student Hemant Kakkar.
Current US Food and Drug Administration (FDA) regulations require that drug ads present a "fair balance" between information about a drug's risks and benefits.
This is typically done by listing all of a drug's side effects and contraindications based on its approved prescribing information. For broadcast ads, FDA gives drugmakers the option of listing only major risks so long as the ad points to a variety of other sources for finding information about the drug, such as referring patients to their doctors, a toll-free phone number or website.
While these regulations are meant to inform consumers about the potential risks of taking a drug, the authors argue that FDA has "paradoxically dampened consumers' judgements of overall severity and risk, and increased the marketability of these drugs."
The authors say this leads to an ethical dilemma between providing consumers with complete information and presenting limited information that could lead to better estimation of risk.
FDA has also recently signaled that it is looking to change its approach to presenting risk information in DTC ads to improve consumers' understanding of risks based on its own research showing that lengthy lists of side effect might lead to worse retention and understanding of a drug's risks.
Under FDA's proposed approach, drugmakers could limit the risks presented in broadcast ads to just those that are severe, serious or actionable, along with a disclosure stating that not all of the drug's risks are listed.
To test their hypothesis, the authors conducted five studies and a meta-analysis comparing about 3,000 subjects' responses to different drug ads that feature either a full list of side effects or only the major ones.
In the first experiment, subjects were played an actual 78 second advertisement for Eli Lilly's anti-depressant Cymbalta (duloxetine) or a trimmed down version 75 second version that omitted three minor side effects.
As the authors predicted, subjects that heard the shorter version with fewer minor side effects rated the drug to be riskier than those who heard the full list, "suggesting that the mention of the minor side effects diluted the perception of the overall severity of the side effects."
The authors rule out lack of attention as a potential explanation for these results, as participants who heard the full ad were able to recall slightly more of the major risks than those who heard the shortened version.
When comparing the two groups, the authors only found a statistically significant positive relationship between the number of risks participants could recall and how severe they rated the overall risk of the drug for those that heard the shorter ad, but not for those that heard the full one.
For patients that heard the full list of side effects, "recalling a higher number of side effects did not increase ratings of drug side-effect severity as their evaluations were ostensibly diluted by the presence of minor side effects," the authors write.
In the next set of experiments, the authors showed participants print ads and other information for three drugs: Lunesta (eszopiclone), Abilify (aripiprazole) and Concerta (methylphenidate), with either a full or abridged set of side effects. In all three experiments, participants hearing only the major side effects rated the drug's risk higher than those hearing all the side effects.
In the final experiment, the authors tested whether emphasizing major side effects could mitigate the dilution effect seen in the other experiments while still presenting a full list of side effects. Here the authors found no difference in risk perception between participants that were given an ad that listed four side effects (two major and two minor) for a fictional drug and those who were shown only the major risks.