Development is necessarily the result of the interdependence, coaction, and/or codetermination among multiple levels of influence over time (Gottlieb, Reference Gottlieb2001). In 1975, Sameroff and Chandler proposed a transactional model of development that recognized the importance of the transacting genetic, constitutional, neurobiological, biochemical, psychological, and sociological factors in the determination of behavior, and that stated that those factors change through their dynamic transaction. Sameroff and Chandler's (Reference Sameroff, Chandler and Horowitz1975) model takes into account the interrelationships among dynamic systems and the processes by which compensatory, self-regulating tendencies are initiated whenever higher level monitors detect deviances in a system (Sameroff, Reference Sameroff2000; Waddington, Reference Waddington1966). An implication of the transactional model is that the continued manifestation of maladaptation depends on environmental support, whereas the child's reciprocal characteristics partially determine the nature of the environment. Thus, an all-encompassing and theoretically meaningful model of development must yield a formulation of the developmental process that can embrace both stability and change. It must transcend the multifaceted ways in which constitutional, organismic, and environmental factors transact to affect development.

By focusing on longitudinal transactional models of development and psychopathology, this Special Issue extends the rich history in Development and Psychopathology of understanding the multiple mechanisms and processes whereby children develop psychopathology or are protected from its development (Cicchetti & Dawson, Reference Cicchetti and Dawson2002). In 2010, a two-part special issue on developmental cascades examined the cumulative effects of influences across levels and areas of functioning, while testing developmental cascade models of change (Masten & Cicchetti, Reference Masten and Cicchetti2010). The articles in that special issue provided new insights into how problems in one domain of functioning might cascade into other domains of functioning. A more recent special issue devoted to multilevel approaches for understanding the development of antisocial behavior (Burnette & Cicchetti, Reference Burnette and Cicchetti2012) included articles describing multiple method, multiple level, longitudinal designs focused specifically on understanding the complex influences on antisocial behavior. These special issues helped answer critical questions in the field regarding the multiple transactional influences on the development of psychopathology. The current Special Issue builds on these advances and focuses specifically on longitudinal models that cut across multiple developmental periods and include three or more time points of data collection, to expand the understanding of transactional models across infancy, childhood, adolescence, and adulthood and examine a larger window of development within each study.

The call for longitudinal models of development, such as those included in this Special Issue, has taken on a global profile, with two recent initiatives led by the National Institutes of Health. Funded in 2015, the Longitudinal Study of Adolescent Brain and Cognitive Development is recruiting 10,000 healthy children age 9–10 and is following them over 10 years into early adulthood, to measure brain maturation in the context of social, emotional, and cognitive development. Similarly, the Environmental Influences on Child Health Outcomes Program at the National Institutes of Health will support multiple longitudinal studies using existing study populations to investigate environmental exposures, including physical, chemical, biological, social, behavioral, natural, and built environments, on child health and development. These two national initiatives will yield rich longitudinal data sets that are ripe for the incorporation of longitudinal transactional models that examine the development of psychopathology across multiple developmental periods and use multilevel sources of data. However, it will be a decade before these large-scale national initiatives are completed and their findings shared with academic and professional audiences. The articles in this Special Issue lay the groundwork for this national work by testing novel hypotheses about the transactional nature of development across time and across environmental and biological contexts by using longitudinal data sets that cut across multiple developmental periods to study development over a decade or more in many cases.

One of the key themes illustrated by the longitudinal analyses presented in the articles in this Special Issue is the great potential for recovery and resilience among children exposed to varied forms of adversity, regardless of whether the adversity stems from experiences in the families that the children have grown up in, their neighborhood environments, their peer networks, their genetic makeup, or in all likelihood, a complex combination of these influences. Further, consistent with bidirectional, transactional models of risk and resilience (Cicchetti & Curtis, Reference Cicchetti and Curtis2007), the articles in this issue provide evidence that children are not simply passive recipients of their environments, but rather, they contribute to their own development in both passive and active ways, by eliciting behaviors from others and by selecting people and contexts within which to interact (e.g., Pardini, Reference Pardini2008; Scarr & McCartney, Reference Scarr and McCartney1983). Further, several papers in this Special Issue use randomized, controlled trial designs to gain further insights into causal mechanisms underlying the development of psychopathology over time. Randomized control trial designs are considered the gold standard for testing causal mechanisms of development and psychopathology and identifying pathways to healthy adjustment, but the articles in this issue add an additional feature: a long-term developmental design. This helps address the significant question in the extant literature of whether programs designed to prevent or reduce psychopathology have sustainable effects in the long term or whether intermediary processes are at play over time that work to either sustain or undermine intervention effects. The long-term intervention follow-up studies in this Special Issue help fill this critical gap in the field in this regard.

Finally, the articles in the Special Issue contribute in important ways to methodological advances relevant to testing models of development and psychopathology. The field has made significant strides over the last decade in developing methodological techniques and approaches to conduct strong tests of longitudinal transactional models of development. This is important because stringent tests of longitudinal models of development and psychopathology should simultaneously consider continuity in behavior, mediational or indirect effects, reciprocal relationships, as well as covariates and potential moderating variables. Thus, longitudinal transactional studies can present serious methodological challenges, particularly when the presentation or expression of psychopathology changes across development, as in the transition from oppositional behavior, to conduct problems, to antisocial behavior. The papers in this Special Issue are exemplary in their incorporation of complex methods for testing mediating and indirect pathways longitudinally (MacKinnon, Reference MacKinnon2008; MacKinnon, Lockwood, & Williams, Reference MacKinnon, Lockwood and Williams2004; Millsap, Reference Millsap2011; Preacher & Hayes, Reference Preacher and Hayes2008; Taylor, MacKinnon, & Tein, Reference Taylor, MacKinnon and Tein2008; Tofighi & MacKinnon, Reference Tofighi and MacKinnon2011) and proposing new methods that account for the fact that transactional mechanisms can produce excess stability in an outcome domain, above and beyond autoregressive processes (see in this issue, Roisman, Fraley, Haltigan, Cauffman, & Booth-LaForce, Reference Roisman, Fraley, Haltigan, Cauffman and Booth-LaForce2016). Methods for handling missing data (Enders, Reference Enders2010), another pesky methodological challenge in longitudinal research, are also rigorously applied across the articles in this Special Issue.

There is a continued need to pursue the development of new theories, methods, and approaches to test complex transactional longitudinal models, and stay abreast of the rapid advances in the measurement of problem behavior if we are to better understand the pathways to, and prevention of, psychopathology. By studying multiple developmental periods and utilizing novel analytic approaches, the articles in this Special Issue represent a highly promising foundation for future longitudinal research in development and psychopathology.