The healthy control subject in psychiatric research: impulsiveness and volunteer bias

Abstract

Exciting and demanding biomedical experiments may attract a specific subgroup of people as volunteers. In the present study of selection bias, subjects volunteering in a psychobiological study that included a potentially painful procedure (lumbar puncture) were compared with those who declined to participate, with regard to scores on personality scales administered during a previous investigation of the same subjects. Significant differences were found on the Eysenck Personality Questionnaire and Karolinska Scales of Personality Impulsiveness scale, suggesting an over-representation of impulsive individuals among the volunteers. If the specific subject of investigation has implications for the type of individual who will participate as a healthy volunteer in biomedical research, variation will be introduced, affecting the independent variable, and the conclusions that can be drawn from such research may be questionable.

Mental and personality disorders as well as personality traits in a Swedish male criminal population

“…Thus, the frequencies reported in the present study are likely to be lower than the true prevalence of mental and personality disorders in male criminals. It has, indeed, been demonstrated that certain personality traits affect the willingness to participate in scienti c studies (44). The present study is descriptive and the general ndings are that substance abuse:dependence and personality disorders are strongly linked to criminal behaviour, which is in agreement with several previous studies both from Sweden and from the US (6 -11, 26, 45-47).…”

Population Reach and Recruitment Bias in a Maintenance RCT in Physically Active Older Adults

“…The new study compared differences in samples recruited with two newspaper advertisements that were nearly identical to the original ad used to recruit for the SPE, except that one ad omitted the topical identifier “prison life.” Compared to those recruited with the more generic ad, volunteers recruited to the “prison life study” scored significantly higher on a number of psychological scales such as aggression, authoritarianism, Machiavellianism and social dominance, and lower on measures of empathy and altruism. Such biases have also been documented in studies of alcohol abuse,11 research on human sexuality,8,12–14 psychiatric research,15,16 and in a handful of physical activity and health promotion intervention studies targeted towards older adults 9,17–24. Although a large number of health promotion initiatives have focused on promoting physical activity (PA) among older populations, with multiple reviews of this literature having been published,25–29 relatively few studies of PA in older adults have investigated volunteer bias, and none have examined the issue in the context of an intervention trial focused on PA maintenance.…”

The Families In Recovery From Stroke Trial (FIRST): Primary Study Results

“…In practice, however, we often enrolled higher-functioning patients who were likely to improve without intervention. This, coupled with a higher refusal rate among more severely affected patients, produced a significant source of volunteer bias (37)(38)(39). Future investigators should consider recruitment and consent procedures that reduce the influence of volunteer bias by recruiting patients who are more like the target population.…”