Academic Articles Pharmaceuticals

Therapeutic non-adherence: a rational behavior revealing patient preferences?

Many studies have revealed patient non-compliance with medical prescriptions (e.g.: not taking prescribed drugs, not visiting the doctor) at around 50%. Most medical researchers believe that non-adherence is either due to 1) irrationality or 2) misinformation. Yet a Health Economics article by Lamiraud and Geoffard (2007) tests the hypothesis of whether or not this behavior may in fact be rational.

Most medical treatments have costs. There are monetary costs, time costs, inconvenience costs, and physical costs from any side affects which occur. Physicians often focus on the benefits of medication without fully taking into account the discomfort patients experience from medication.

To solve this problem the authors used a data from a randomized controlled trial (RCT) of HIV-1 infected patients. The trial aimed to test the safety and efficacy of two HAART therapies. The authors use the following system of equations to estimate factors associated with compliance.

  • θ*it=x1itβ11it
  • h*it=x2itβ2+ θitγ +ε2it
  • εjitjtjit

The variable θ* represents a latent variable as to the level of adherence (θ=1 for full adherence and 0 otherwise) and h* is a latent variable representing the health status of the individual (h=1 if the individual is an a good health status and 0 otherwise). The model is estimated using a panel non-linear simultaneous two-equation system.

The authors find that higher adherence levels are associate with higher patient welfare. Thus, if two drugs are equally effective, the authors recommend that policy-makers, insurance companies, and government should select the pharmaceutical with higher compliance levels. “To the contrary, the clinicians of the trial were tempted to support the treatment in which the adherence level was smaller, based on the rationale that a higher adherence would have pushed the efficacy to upper levels in that group.”

Realizing that adherence is an endogenous behavior made by rational individuals may change the way in which the benefits of prescription drugs are measured in the future.