Developmental co-occurrence of psychopathology dimensions in childhood: between and within person processes

BackgroundComorbidity between psychopathologies may be attributed to genetic and environmentaldifferences between people as well as causal processes within individuals, where onepathology increases risk for another. Disentangling between-person (co)variance fromwithin-person processes of psychopathology dimensions across childhood could shed light ondevelopmental causes of comorbid mental health problems. Cross-sectional data as well asstandard models to investigate lagged effects conflate between-person and within-personprocesses. This makes it difficult to distinguish time invariant overarching (confounding)factors from temporal directed effects. Additionally, more recent random effects modelsmake no allowance for direct temporal effects from one person to another. Here, we aim todetermine whether and to what extent directional relationships between psychopathologydimensions within-person, and between individuals within families, play a role inmultivariate comorbidity.MethodsWe investigated longitudinal data on measures of common psychopathologies fromchildhood to early adolescence (age 7 to 12), jointly estimating between-person and withinpersonprocesses across time. We conducted random intercepts cross-lagged panel model(RI-CLPM) analyses to unravel the longitudinal co-occurrence of child psychopathologydimensions, and developed an extension of the model to estimate sibling effects withinfamily(wfRI-CLPM). Analyses were separately conducted in two large population-basedcohorts, the Twin Early Developmental Study and the Netherlands Twin Register, includingparent-rated measures of child problem behaviours based on the SDQ and CBCL scalesrespectively.ResultsWe found evidence for strong between-person effects underlying the positive intercorrelationbetween problem behaviours across time. We further identified time-varying within-personprocesses accounting for an increasing amount of trait variance overtime, up to 11% forattention problems in TEDS, and up to 18% for attention problems and social problems inNTR. Lastly, by accommodating family-level data, we found evidence for reciprocaldirectional influences within sib-pairs longitudinally, from externalizing to internalizingproblems, after accounting for similarities that arise through shared (genetic orenvironmental) influences.Co-occurrence of psychopathology dimensions in childhoodConclusionsOur results indicate that within-person processes partly explain the co-occurrence ofpsychopathology dimensions in childhood, and within families, suggesting that both shouldbe taken into account in developmental models of comorbidity.

The Effect of the Free Primary Education Policy on School Enrolment and Relative Grade Attainment in Lesotho†

We examine the impact of Lesotho’s Free Primary Education (FPE) programme on enrolment and relative grade attainment. The programme was sequentially implemented by first abolishing school fees in grade one in the year 2000. The timing of the implementation created changes in programme coverage across age groups over time. We employ a difference-in-differences strategy that exploits these variations to identify the effects of the FPE policy. Using data from the 2000 Multiple Indicator Cluster Survey and the 2002 Core Welfare Indicators Questionnaire survey, we find that the FPE policy increased enrolment of primary school-age children by 19.1 percentage points between 1999 and 2002. We also find that the policy had a negative effect on relative grade attainment: post-FPE, children had 0.15 fewer grades per year of age compared to pre-FPE. We do not find evidence of sibling effects.