Current Medical Diagnosis & Treatment in Psychiatry

Developmental Concepts

Moderators & Protective Factors

Rutter has enlightened scholars that the effect of a risk factor on a disorder may vary across contexts, populations, or circumstances. That is, the magnitude of an effect might be reduced (or enhanced) under different conditions. For example, the effect of early harsh discipline on the development of conduct disorder is reduced under circumstances of a warm parent-child relationship. This phenomenon is called a moderator effect and is defined by a significant interaction effect between a risk factor and a moderating factor in the prediction of a disorder.

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Mediators & Process

Developmental psychologists study the causal process through which disorder develops. The identification of a risk factor does not necessarily imply a causal process, because (1) a risk factor might be a proxy for a causal factor and empirically related to a disorder only because of its correlation with this causal factor (the so-called third-variable problem), (2) a risk factor might occur as an outcome of a process that is related to a disorder rather than the antecedent of the disorder, or (3) a risk factor might play a causal role in a more complex, multivariate process. Therefore, developmental psychologists often attempt to understand the process through which risk factors are related to eventual disorder. The factors that are identified as intervening variables in this process are called mediators, which are defined as variables that account for (or partially account for) the statistical relation between a risk factor and a disorder.

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Risk Factors & Vulnerability

Epidemiologic and developmental researchers have introduced the notion of risk factors to identify variables known to predict later disorder. A risk factor is defined by its probabilistic relation to an outcome variable, without implying determinism, early onset of disorder, or inevitability of outcome. Risk factors are either markers of some other causal process or causal factors themselves. One goal of developmental research is to determine the causal status of risk markers. As noted earlier in this chapter, social competence, or level of adaptive functioning, is a broad risk factor for many disorders, but empirical research must determine whether this factor merely indicates risk that is caused by some other factor (eg, genes) or constitutes a contributing factor in itself.

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Risk Factors & Vulnerability

Epidemiologic and developmental researchers have introduced the notion of risk factors to identify variables known to predict later disorder. A risk factor is defined by its probabilistic relation to an outcome variable, without implying determinism, early onset of disorder, or inevitability of outcome. Risk factors are either markers of some other causal process or causal factors themselves. One goal of developmental research is to determine the causal status of risk markers. As noted earlier in this chapter, social competence, or level of adaptive functioning, is a broad risk factor for many disorders, but empirical research must determine whether this factor merely indicates risk that is caused by some other factor (eg, genes) or constitutes a contributing factor in itself.

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Adaptation & Competence

Research in developmental psychology has sometimes enabled sharper distinctions between normal and abnormal (such as when a genetic marker of a disorder is identified), but more often it has articulated the continuity between normal and abnormal. Research has suggested that disorders might be defined less by noncontextualized behavioral criteria (eg, a score on an IQ test) and more by an assessment of the individual’s level of adaptation and functioning. This concept has been embraced by the term competence, or adaptive functioning, which is the level of performance by an individual in meeting the demands of his or her environment to the degree that would be expected given the environment and the individual’s age, background, and biological potentials.

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Importance of Context

One of the most important contributions of developmental psychology has been the discovery that patterns of behavior, and of process-behavior linkage, vary across contexts. In the context of U.S. society, a child who is teased by peers might find support for retaliating aggressively, whereas the same teasing experience in Japanese society might well cause shame, embarrassment, and withdrawal. Context shapes single behaviors and may also shape patterns of psychopathology.

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Major Principles of Ontogeny & Phylogeny

Cairns and Cairns outlined seven principles that characterize the human organism in interaction with the environment over time: conservation, coherence, bidirectionality, reciprocal interaction, novelty, within-individual variation, and dynamic systems. The first principle is that of conservation, or connectivity in functioning across time. Even with all the pressure to change, social and cognitive organization tends to be continuous and conservative. The constraints on the organism and the multiple determinants of behavior lead to gradual transition rather than abrupt mutation. Observers can recognize the continuity in persons across even long periods of time; that is, we know that a person remains the same “person.” For Piaget, who began his career by writing scientific papers on the evolution of mollusks, this within- person continuity principle is consistent with his view that species-wide evolution is gradual. Piaget believed that development within individuals reflects development of the species (ie, ontogeny recapitulates phylogeny).

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Critical Periods & Transition Points

A critical period is a point in the life span at which an individual is acutely sensitive to the effects of an external stimulus, including a pathogen. Freud argued that the first 3 years of life represent a critical period for the development of psychopathology, through concepts such as regression, fixation, and irreversibility. The concept of critical stages gained credence with studies of social behavior in animals by the ethologist Lorenz and the zoologist Scott. This concept is part of several central theories of social development, such as Bowlby’s attachment theory (discussed later in this chapter). The rapid development of the nervous system in the first several years, coupled with relatively less neural plasticity in subsequent years, renders this period critical. The effects of exposure to lead and alcohol, for example, are far more dramatic when the exposure occurs in utero or in early life than later.

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Age Norms

A simple but powerful developmental concept that has affected psychiatric nosology is that of age norms. Rather than evaluating a set of behaviors or symptoms according to a theoretical, absolute, or population-wide distribution, diagnosticians increasingly use age norms to evaluate psychiatric problems. Consider the evaluation of temper tantrums. In a 2-year-old child, tantrums are normative, whereas in an adult, angry outbursts could indicate an intermittent explosive disorder or antisocial personality. More subtle examples have begun to affect the diagnosis of many disorders in the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV), such as attention-deficit/hyperactivity disorder, mental retardation, and conduct disorder. With regard to major depressive episodes and dysthymic disorder, age norming has resulted in consideration of different symptoms at different ages in order to diagnose the same disorder (eg, irritability and somatization are common in prepubescent depression, whereas delusions are more common in adulthood). DSM-IV explicitly requires consideration of age, gender, and culture features in all disorders, suggesting the importance of evaluating symptoms within the context of their expression.

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Biosocial Interactions

Not only are multiple distinct factors implicated in the genesis of a disorder, the profile of factors often conspires to lead to psychopathologic outcomes. Empirically, this profile is the statistical interaction between factors (in contrast with the main effects of factors). Thus a causal factor might operate only when it occurs in concert with another factor. For example, the experience of parental rejection early in life is a contributing factor in the development of conduct disorder but only among that subgroup of children who also display a biologically based problem such as health difficulties at the time of birth. Likewise, health problems at birth do not inevitably lead to conduct disorder; the interaction of a biologically based predisposition with a psychosocial stressor is often required for a psychopathologic outcome.

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Multiple Pathways

One vexing problem highlighted by research in developmental psychology is that some disorders involve multiple etiologic pathways. The principles of equifinality and multifinality, derived from general systems theory, hold for many disorders. Equifinality is the concept that the same phenomenon may result from several different pathogens. For example, infantile autism results from congenital rubella, inherited metabolic disorder, or other factors. Multifinality is the concept that one etiologic factor can lead to any of several psychopathologic outcomes, depending on the person and context. Early physical abuse might lead to conduct disorder or to dysthymic disorder, depending on the person’s predilections and the environmental supports for various symptoms; poverty predisposes one toward conduct disorder but also substance abuse disorder.

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Developmental Trajectories

Diagnosticians must consider not only the age-normed profile of symptoms but also the developmental trajectories of those symptoms (both age-normed and individual). For example, consider three 10-year-old children who exhibit aggressive behavior. As depicted in Figure 1-1, child A has displayed a relatively high rate of aggression historically, but the trajectory is downward. Child B has displayed a constant rate of aggressive displays, and child C’s aggressive displays have accelerated geometrically. Which child has a problematic profile? The diagnostician will undoubtedly want to consider not only current symptom counts (in relation to age norms) but also the developmental trajectory of these counts (and the age norm for the trajectory). Child C might be most problematic because of the age trend, unless this trend were also age normative (eg, some increase in delinquent behavior in adolescence is certainly normative). In contrast, child B’s constant pattern might be problematic if the age-normed trend were a declining slope.

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Boundary between Normal & Abnormal

One of the tenets of developmental psychology is that a knowledge of normal development informs psychopathology partly because the boundaries between normal and abnormal are sometimes vague, diffuse, or continuous. Many disorders (eg, conduct disorder, dysthymic disorder) are defined on the basis of cutoffs in dimensional criteria rather than on qualitative distinctions that are more easily recognizable. Criteria such as “low energy” and “low self-esteem” (for dysthymic disorder) and “marked or persistent fear” (for social phobia) are matters of degree. One of the central questions is where to locate the boundary between normal and abnormal when the criteria of psychopathology are dimensional.

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Developmental Concepts

The concept of development forms the backbone of modern behavioral science. Psychiatric practitioners and behavioral scientists are concerned primarily with change, and developmental psychology is the scientific study of the structure, function, and processes of systematic change across the life span. Even systems of classification of behavior (including psychiatric nosology) take into account not only contemporaneous features and formal similarities among current symptoms but also past qualities, immediate consequences, and long-term outcomes.

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