Introduction

In the last two decades cognitive-clinical psychology has made impressive gains in the scope of its application to diverse clinical disorders, the complexity of its theoretical formulations, and the sophistication of its research methodology. If one were to compare current cognitive theory, research and treatment with the earliest writings of Beck (1967), Ellis (1962), Meichenbaum (1977), Rehm (1977) and Mahoney (1974), there can be little doubt that we have come a long way from those first forays into the cognitive basis of psychological disorders. If one ever questioned whether cognitive therapy (CT) represented a paradigmatic shift in clinical psychology (Wilson, 1978), a look back over the last 20 or 30 years of research and treatment advances should dispel any doubt.

As evident from the chapters in the current volume, correlational and experimental investigations into the cognitive basis of clinical disorders represents a prominent research perspective that is evident across a wide range of psychological problems. Moreover, the basic elements of CT and cognitive-behavioral therapy (CBT) have been applied to a diverse group of disorders in children, adolescents, and adults. We have a much better understanding of the cognitive concomitants of certain clinical disorders, and of the role of cognition in the etiology, persistence, and severity of disorders. The more scientific and rigorous experimental methodology of information processing has been employed to test various cognitive hypotheses.

Important advances have been made in the field of cognitive therapy during the past 30 years, and numerous books have been published describing the application of these models to a range of clinical problems and populations. The ascent of cognitive therapy has been rapid and, in many ways, quite remarkable. It has become an integral part of training in psychiatry and clinical psychology, and has emerged as a dominant paradigm for understanding psychopathology and psychosocial intervention. Even a brief perusal of the contents of contemporary journals attests to the strength and breadth of these approaches.

How did this come about? Cognitive therapy emerged during the late 1950s and early 1960s as the result of the convergence of several historical trends (Mahoney, 1991; Clark and Beck, 1999; Dobson and Dozois, 2001). These included: (1) a growing recognition of the importance of information-processing models in linguistics and experimental cognitive psychology; (2) the publication of studies supporting mediational models of human adaptation, and the emergence of social learning theory as a paradigm for understanding the development of psychopathology; (3) a growing dissatisfaction with traditional drive models of human motivation and the dearth of empirical support for the effectiveness of psychodynamic forms of psychotherapy; and (4) a recognition of limits of classical behavioral models for understanding human development. Cognitive therapy emerged, then, in response to social needs, and as a result of a growing recognition of the limitations of existing models.

Depression is a significant problem among children and adolescents, with 2-5% of the population meeting diagnostic criteria for this disorder at any point in time (Fleming and Offord, 1990; Lewinsohn et al., 1993; Boyd et al., 2000). The percentage of young people affected by disorders of mood is even higher if one includes dysthymia and bipolar spectrum disorder or if we consider those who report symptoms of dysphoria but who do not meet criteria for the full clinical syndrome. The prevalence of clinical depression increases with age, being less common in preschool and primary (elementary) schoolchildren, and increasing in midadolescence. Community prevalence rates for affective disorders among schoolchildren are relatively low, ranging from 0.4% to 2.5% (Anderson et al., 1897; Kashani and Ray, 1983; Costello et al., 1988; Kashani et al., 1989). Depression is more common, however, among adolescents, with community prevalence rates ranging from 2.9% to 8% (Kashani et al., 1987; Lewinsohn et al., 1993). By the age of 18 years approximately 20% of young people will have experienced at least one episode of a depressive disorder. Moreover, 1-6% of adolescents manifest a depressive disorder at any given time (Fleming and Offord, 1990; McCracken, 1992).

In addition to the relatively high prevalence of clinical depression in young people, there are several reasons we need to take this problem seriously. First, there are a range of short-term negative consequences associated with depression, including disruption to personal relationships and school performance (Kellam et al., 1991; Petersen et al., 1993).