“Feeling down…feeling irritable…trouble getting up in the morning?....Depression hurts….Drug X can help….speak to your doctor about Drug X…”.  These 60 second appeals are a ubiquitous part of the US television experience. This is because, in the US, pharmaceutical companies can lawfully market prescription medications to the public through direct to consumer (DTC) advertising. Critics have charged that doctors should decide prescription medications without being influenced by patient requests. Citing the proliferation of DTC ads as the main culprit for increasing patient demand for advertised drugs, the American Medical Association has advocated for a ban on DTC ads. But the pharmaceutical companies argue that patients have the right to know their options and thus would benefit from these commercials. 

The ability to market prescription drugs creates an incentive for the pharmaceutical companies to amplify the benefits of the drugs without discussing its potential side effects. To counteract this, in 1997, the Food and Drug administration (FDA), regulated these ads by stipulating a fair balance between the benefit and risk (i.e., side effects and contraindications) associated with the drug. The space allotted on print media and air time on broadcast media, to listing the risks/side effects should be equivalent to the space and time allotted to its benefits. The assumption is that listing all side effects of the drug balances an inflated impression of the drug’s efficacy allowing consumers to make an informed decision. 

However, the FDA’s assumption that more risk information leads to greater concern about risk is misplaced. Across six experiments, comprising of over 3000 US participants, we reliably find that when drug commercials include all side effects (both major and minor), in line with the FDA’s regulations, consumers’ judged the overall severity of drug side effects to be lower than when exposed to only major side effects. This lowered assessment of severity led consumers to prefer the drug more—and made them willing to pay more for the drug.

It is well established that people are susceptible to a range of cognitive and psychological biases that stray decisions from rationality. One such bias is the argument dilution effect. This bias is especially consequential when making social and non-social judgements about a target with an array of information that is both relevant and non-relevant to the decision.  In such situations, our conclusions about the target are roughly based on averaging both the relevant and non-relevant information, instead of ignoring the non-relevant information. In other words, the non-relevant information dilutes the value and importance of the relevant information. Initially documented by Richard Nisbett and colleagues, its ubiquity in impacting social and non-social judgements is well-established. For instance, imagine having to assess the GPA of the following two students. You are either told; “Tim spends 31 hours studying outside of class in an average week” or “Tom spends 31 hours studying outside of class in an average week. Tom has one brother and two sisters. He visits his grandparents once every 3 months. He once went on a blind date. He shoots pool once every 2 months.”  When participants in a study by Zukier were presented with these options, Tim was rated as having a significantly higher GPA than Tom. The irrelevant information around Tom’s grandparents and his casual play of pool, “diluted” the value and importance of the relevant information—his study habits. 

We wanted to know if the dilution effect also plays a role in DTC commercials. The FDA regulation to list all potential side effects of the drugs in a DTC commercial inadvertently resulted in these commercials describing both major (e.g., stroke, heart-attack, thoughts of suicide) and comparatively minor (e.g., dry mouth and headache) side effects. Building on argument dilution as the underlying psychological bias, we hypothesized that listing both major and minor side effects would dilute consumers’ judgements of the overall severity of the drug’s side effects compared to when only major side effects are presented.

In one experiment, American participants heard an audio commercial for the drug Cymbalta—a drug that treats depression and marketed via DTC advertising. Half the participants heard the original commercial in entirety (78 seconds), while the other half heard a 4% shorter commercial (75 seconds), which removed mention of the three minor side effects. Those who heard the commercial in entirety rated the drug lower in its overall severity of side effects compared to those who heard the 4% shorter version of the commercial. In addition, the lower overall assessment of severity increased the attractiveness of the drug in comparison to those who heard the shorter commercial. 

A follow-up study employed a different advertising medium by having participants read an actual print ad for the drug Lunesta, which is used to treat sleep disorders.  Once again, half the participants read the entire ad which included four side effects (2 major and 2 minor), while the other half read an ad that included just the 2 major ones.  Again, reading the ad with more side effects, including minor ones, caused participants to rate the drug less in overall severity and rate the drug as more appealing.

These findings raise the ethical and practical dilemma of achieving transparency with the consumers by sharing all potential side effects, while safe-guarding them against the argument dilution bias.  Hence, we performed an additional study to explore how this might be achieved. If individuals can cognitively place greater weight to the major side effects than the minor ones, the averaging process of the argument dilution effect, should attenuate. Thus, to draw greater attention and emphasis to the major side effects, we listed these side effects in a red bold font and minor ones in a black regular font. Participants who saw major and minor side effects in different fonts rated the drug similar in severity compared to those who only saw the major side effects. Thus, by drawing greater attention to the major side effects, we were able to overcome the argument dilution effect while ensuring all side-effects associated with the drug are communicated to consumers.

With an annual industry spend of over 5 billion dollars on DTC ads, it is not surprising that these ads have resulted in increased patient demands for the drugs featured in the ads. These results add to the chorus for the redrafting of policies surrounding the communication of risk of pharmaceutical drugs. More broadly, this work draws caution to other forms of risk communication that extends beyond DTC: physicians who have to communicate varying risks of an experimental procedure, financial advisors who need to make retirees aware of various perils in the financial products they intend to invest in, to public service advertisements that attempt to highlight the risk associated with life choices.