thesisEmerging research investigating psychophysiological and neurobiological indicators of posttraumatic stress disorder (PTSD) suggests that posttraumatic stress symptoms (PTSS) may be characterized by two distinct symptom patterns, termed overmodulation and undermodulation. However, little of this research has been conducted among youth, and none has directly investigated whether psychophysiological responses may serve as indicators of these forms of affect dysregulation. To address this gap in the literature, this study investigated whether the over- versus undermodulation patterns emerged among a sample of 822 detained adolescents (185 girls, 596 boys) and tested whether autonomic stress reactivity and recovery reliably corresponded to patterns of emotional over- and undermodulation. Among boys in the sample, three profiles emerged that largely reflected low PTSS, overmodulation, and undermodulation; among girls in the sample, only two profiles emerged, reflecting low PTSS and overmodulation. However, class membership for boys and girls was not associated with distinct patterns of physiological response. The current findings offer evidence that symptom patterns of over- and undermodulation may be distinguishable in youth but do not yet provide support for physiological indicators of these profiles