Where did all the pathological gamblers go? Gambling symptomatology and stage of change predict attrition in longitudinal research.

Attrition can introduce a systematic bias that can negatively affect validity (Cook and Campbell, Quasi-experimentation: design and analysis issues for field settings. Rand McNally, Chicago, 1979). Current longitudinal research in gambling, however, has generally overlooked the reasons for attrition. The current research examined the relationship between pathological gambling symptomatology, stage of change and attrition. Three hundred and seventy-nine participants were contacted 12 months after initially participating in a study on gambling for a follow-up session. Logistic regression revealed those in the contemplation and preparation stages of change reported higher levels of pathological gambling symptomatology and were more likely to drop out of the study compared to those in the precontemplation stage. As predicted, gambling symptomatology mediated the relationship between stages of change and attrition. The implication for longitudinal research on gambling as well as extant findings that have used this methodological approach is discussed.