Selective drop-out in longitudinal studies and non-biased prediction of behaviour disorders

Abstract

BackgroundParticipant drop-out occurs in all longitudinal studies, and if systematic, may lead to selection biases and erroneous conclusions being drawn from a study.AimsWe investigated whether drop out in the Avon Longitudinal Study of Parents And Children (ALSPAC) was systematic or random, and if systematic, whether it had an impact on the prediction of disruptive behaviour disorders.MethodTeacher reports of disruptive behaviour among currently participating, previously participating and never participating children aged 8 years in the ALSPAC longitudinal study were collected. Data on family factors were obtained in pregnancy. Simulations were conducted to explain the impact of selective drop-out on the strength of prediction.ResultsDrop out from the ALSPAC cohort was systematic and children who dropped out were more likely to suffer from disruptive behaviour disorder. Systematic participant drop-out according to the family variables, however, did not alter the association between family factors obtained in pregnancy and disruptive behaviour disorder at 8 years of age.ConclusionsCohort studies are prone to selective drop-out and are likely to underestimate the prevalence of psychiatric disorder. This empirical study and the simulations confirm that the validity of regression models is only marginally affected despite range restrictions after selective drop-out.

Peer Victimization in Childhood and Internalizing Problems in Adolescence: A Prospective Longitudinal Study

“…Although the prevalence of depressive disorder is low in early adolescence (Costello et al 2006;Shanahan et al 2011), the prevalence of DAWBA-assessed depression and anxiety diagnoses in 13-15 year olds has been shown to be respectively 2.5% and 5%, in a nationally representative UK sample (Ford et al 2003). These figures are higher than in this study, which could be explained by selective drop out: the ALSPAC participants who consistently participated were less likely to have a psychiatric diagnosis (Wolke et al 2009a). …”

“…Indeed power was limited for DSM-IV diagnoses. In contrast, the relationship between predictors and depression symptoms is unlikely to have been substantially altered by selective dropout processes as has been shown in simulations (Wolke et al 2009a), nevertheless it cannot be ruled out.…”

“…The aim was to study prospective relationships rather than prevalence estimations that require complete populations. Thus no missing value imputations were conducted (Wolke et al 2009a). …”

Pathways from maternal depressive symptoms to adolescent depressive symptoms: the unique contribution of irritability symptoms

“…As these predictors of attrition also predict child psychopathology, our sample is likely to under‐represent the most severely affected children. Of note, an ALSPAC cohort study (Wolke et al., 2009) has shown that attrition affects the prevalence of DSM‐IV disruptive behavior disorders (which includes ODD), however, associations between risks and outcomes remained present, although conservative of the likely true effects. Fifth, although the ALSPAC sample represents a broad spectrum of SES backgrounds, it includes relatively low rates of ethnic minorities.…”

Involvement in Bullying and Suicide-Related Behavior at 11 Years: A Prospective Birth Cohort Study

“…51 "True" relationships between an exposure (i.e. role in bullying) and outcome (suicidal ideation or suicidal/self-injurious behavior) should be found irrespective of whether they are investigated in more, or less, advantaged sections of the population.…”