Hello-Goodbye Effect

The Hello-Goodbye Effect refers to the bias caused by patients who exaggerate their problems before a[Page 430] treatment (or any intervention), hoping to be eligible for the therapy, and minimize their problems at the end of the treatment, hoping to please the therapist. The Effect has two components. The first is related to the Faking Bad Bias, whereby participants try to appear sick to qualify for support. The second is related to the Faking Good Bias (or Social Desirability Bias or Obsequiousness Bias), whereby participants may systematically respond in the direction they perceive to be desired by the investigator.

An example of the Hello-Goodbye Effect is found in a review of pain measures of patients before and after acupuncture treatment. Pain is the most frequent complaint of patients referred for acupuncture. However, it is difficult to measure because it cannot be measured directly and must be measured on the basis of the patients' response. For example, the patient may be asked to select from five pain categories ranging from none to intense or from a numerical rating scale ranging from 0 to 10. Results of the measurement can be greatly influenced by the individual's genotype, culture, conditioning, education, and so on. The review suggested that, when patients first present for treatment, they need to justify their request for help, so there is a subconscious tendency to exaggerate symptoms. After patients have received treatment, they may want to please the therapist, or at least not hurt the therapist's feelings, so there is a tendency to minimize symptoms.

The Hello-Goodbye Effect may result in surprising improvements in the symptoms after a treatment. In extreme cases, even totally ineffective treatments can produce an improvement in treatment results.

In clinical practice, it is difficult to prevent or minimize the Hello-Goodbye Effect. But in research, it can be minimized by letting participants know that the information they provide (as recorded on the forms or questionnaires) will not be seen by the therapist.

One must be careful not to confuse the Hello-Goodbye Effect with other, distinctly different effects, which in some cases may produce similar outcomes. These effects may include Apprehension Bias (certain measures may alter systematically from their usual levels when the participant is apprehensive; e.g., blood pressure may change during medical interviews); Attention Bias (or the Hawthorne Effect; study participants may systematically alter their behavior when they know they are being observed); Culture Bias (participants' responses may differ because of culture differences); and the placebo effect (measurable, observable, or felt improvement in health attributable not to treatment but to a placebo, which is a medication or treatment believed by the therapist to be inert or innocuous).