Where Have All the Worriers Gone? Temporal Instability of the Abbreviated Penn State Worry Questionnaire Limits Reliable Screening for High Trait Worry

Abstract

Participant selection is an important step in research on individual differences. If detecting an effect of a personality variable is predicated on the use of extreme groups, then mistakenly including participants who are not in the extremes may weaken the ability to see an effect. In this study, changes in trait worry were evaluated in 68 undergraduate students reporting low or high levels of worry. Participants completed the abbreviated Penn State Worry Questionnaire (PSWQ-A) three times: 1) at the beginning of the se- mester; 2) 3 - 13 weeks later; and 3) 1 hr later, following a psychophysiological assessment session. Test–retest reliability across the three administrations was high, but almost half of the sample no longer met the pre-defined criteria for classification as low or high worriers at the second administration. That is, scores were reliable, but not stable, across time. Instability of self-report worry was significantly greater for high worriers than for low worriers, and this effect was predicted by trait anxiety at the beginning of the semester. These findings suggest that the PSWQ-A is sensitive to factors other than trait worry, which may result in dilution of effects when participants are selected for extreme worry scores. This also sug- gests that screening participants weeks before the actual study should be supplemented by readministra- tion of the screening questionnaire, to identify participants who no longer meet criteria for inclusion.