Current Medical Diagnosis & Treatment in Psychiatry

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.

An alternative to the concept of a critical period is the hypothesis of gradually decreasing plasticity in functioning across the life span. As neural pathways become canalized, mental representations become more automatic and habits form. However, the notion of the primacy of early childhood has been thrown into question by empirical data that indicate greater malleability in functioning than was previously thought. Rutter, for example, suggests that a positive relationship with a parental figure is crucial to the prevention of conduct disorder and that this relationship can develop or occur at any point up to adolescence, not just during the first year of life.

Some developmental psychologists have argued for other critical periods in life, such as puberty and giving birth as critical periods for the development of major depressive disorder in women, although this assertion has been contested. Critical periods might be defined not only by biological events but also by psychosocial transitions. Developmental psychologists have increasingly recognized the crucial role of major life transitions in altering developmental course, accelerating or decelerating psychopathologic development, and representing high-risk periods for psychopathology. These transition points include but are not limited to entry to formal schooling, puberty and the transition to junior high school, high school graduation and entry into the world of employment, marriage, birth of children, and death of one’s loved ones (particularly parents or spouse). These transitions have been associated with elevated risk for some forms of psychopathology. One task of developmental psychologists is to discover which life transitions are most crucial and how these transitions alter the course of development of some but not other forms of psychopathology.

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