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Social Stress, Affect, and Neural Function 221dangerous events or circumstances; across species, organisms that effectivelyrecognize and react to danger tend to enjoy enhanced fitness. Among humans,typical development involves the emergence of a relatively stereotyped patternof fears or worries that tend to serve adaptive purposes (Marks, 1987; Muriset al., 2000). For example, fears of strangers and of separation become evident innormally developing preschoolers across many cultures. Additionally, adolescentsshow a normative increase in concerns about scrutiny from peers or adults. Suchincreases in anxiety, which can be associated with marked discomfort, are a featureof healthy development at key stages of life. Consequently, it can be difficult toidentify the point at which anxiety crosses the line into pathological manifestations.Two criteria, sometimes referred to as the “impairment” and “distress” criteria,form the basis on which distinctions between normal and pathological anxiety aretypically made. First, anxiety is considered pathological when it disrupts functioningand interferes with the successful completion of daily living tasks. Thus,shyness becomes pathological when it leads an adolescent to avoid social situationsor events that most peers would not avoid. Second, anxiety is consideredpathological when the degree of distress is extreme, in terms of intensity, frequency,and duration.Although these criteria provide guidelines for distinguishing healthy frompathological anxiety, they remain controversial. In particular, practitioners debatewhether severity of distress should serve as an index of pathology. To evaluatedistress, a clinician must determine whether an adolescent’s subjectivelyreported internal state is within the expected range for youth of similar age. Suchsubjective ratings are potentially fraught with bias and influenced by varyingcultural or family standards, which raises questions about whether this criterionforms a valid basis for classifying youth into diagnostic groups. Moreover, althoughthe “impairment” criterion is less likely to be affected by the biases inherent inapplications of the “distress” criterion, it too is problematic. For example, relativelysubtle variations in the rules for applying the impairment criterion exertprofound effects on prevalence estimates, particularly for adolescent anxiety disorders(Shaffer et al., 1996).This controversy is not surprising, given the state of psychiatric nosology.Current nosological classifications, as articulated in DSM-IV, are based on clinicalassessments that rely heavily on reports of symptoms from patients and relevantinformants, such as parents. Use of this classification system has led tomarkedly better diagnostic reliability than was possible using earlier classificationschemes. This increase in reliability has, in turn, introduced much-neededstandards into mental health care. Nevertheless, as the science of mental illnessmatures, it seems plausible and desirable that diagnosis will eventually be basedon an understanding of pathophysiology. In particular, laboratory-based assessmentsof brain dysfunction have the potential to provide a more objective or atleast a corroborative index of mental status. Unfortunately, the field is many years