Longitudinal research in pediatric psychology: an introduction to the special issue.

This issue of the Journal of Pediatric Psychology (JPP) includes articles submitted for a special issue on “Longitudinal Research in Pediatric Psychology.” In the Call for Papers, we sought empirically oriented manuscripts that employed longitudinal designs and theoretical, methodological, or statistical papers relevant to longitudinal research. Examples of potential topics were provided in the Call and included: (a) familial, peer, and/or other contextual predictors of subsequent change in health-compromising behaviors in typically developing children or change in health-related behaviors and processes in children with chronic illness, (b) the impact of chronic illness on normative development or the consequences of varying developmental trajectories for subsequent health-related behaviors and processes, (c) studies that isolate different health trajectories as well as predictors of such differential outcomes, (d) tests of prospective mediational or causal predictor models based on longitudinal data, and (e) prevention, health promotion, and intervention studies with multiple data collection points that identify intervening mechanisms of change in health outcome. In response to the Call for Papers, 15 manuscripts were submitted. This issue includes eight of these articles; the first focuses on statistical strategies that can be used with longitudinal data and the other seven papers are empirical studies. Longitudinal studies permit examination of changes in health-related behaviors and processes over time. Such designs can be retrospective or prospective, with the latter having clear advantages over the former (Loeber & Farrington, 1994). As will be argued in more detail below, prospective longitudinal investigations of children with chronic physical conditions may be particularly informative when change is examined during critical developmental periods or transition points (e.g., early childhood, the transition to school, the early adolescent transition, the transition to adulthood). Indeed, a chronic condition is “chronic”; the impact of the condition is likely to unfold over time. At the most complex level of analysis, the task for the researcher is to understand a chronic condition that is changing over time in an individual that is also changing, developing, and maturing over time. Despite the advantages of longitudinal designs in addressing such issues, most studies in the fields of clinical child psychology and pediatric psychology are not longitudinal. In an earlier special issue of the Journal of Consulting and Clinical Psychology (JCCP) on “The Role of Longitudinal Data with Child Psychopathology and Treatment,” Wierson and Forehand (1994) conducted a review of articles published on children and adolescents between 1983 and 1992 and found that only 4% were longitudinal (with 13% of those in JCCP being longitudinal). Of course, not all research questions require longitudinal designs, but Wierson and Forehand’s (1994) review suggests that such designs are more the exception than the rule. Within the field of pediatric psychology (and in JPP, in particular), most scholars suggest in their “future directions” sections that longitudinal data would be beneficial. Indeed, Wallander and Varni (1998) argued that developmentally oriented longitudinal studies in the field of pediatric psychology would be informative: “General developmental processes should become more salient features of the conceptualizations of adjustment in this special group. Longitudinal designs need to become the norm” (p. 42). In this introductory article, we first discuss advantages of longitudinal research in the study of children and adolescents with chronic conditions. Next, we provide an overview of several factors one may wish to consider when designing longitudinal studies with pediatric populations. Finally, we provide a brief overview of the articles included in this special issue.