- BACKGROUND: Few studies have examined stress reactivity and its relationship to major depressive disorder (MDD) and posttraumatic stress disorder (PTSD) among maltreated youth. We examined differences between maltreated and control participants in heart rate and cortisol resting and reactivity levels in response to a psychosocial stressor. METHODS: We recruited 67 female youths aged 12 to 16 with no prior history of depression from child protection agencies and a control group of 25 youths matched on age and postal code. Child maltreatment was measured with two self-report instruments. Psychiatric status was assessed using the Schedule for Affective Disorders and Schizophrenia for School-Aged Children. RESULTS: Piecewise multilevel growth curve analysis was used to model group differences in resting and reactivity cortisol levels and heart rate in response to the Trier Social Stress Test (TSST). During the resting period, both the maltreated and control groups showed a similar decline in levels of cortisol. During the reactivity phase, youth in the control group showed an increase in cortisol levels following the TSST and a gradual flattening over time; maltreated youth exhibited an attenuated response. This blunted reactivity was not associated with current symptoms of MDD or PTSD. There were no group differences in resting and reactivity levels of heart rate. CONCLUSIONS: These findings provide further support for hypothalamic-pituitary-adrenal axis dysregulation among maltreated youth. Since the ability to respond to acute stressors by raising cortisol is important for health, these findings may assist in understanding the vulnerability of maltreated youth to experience physical and mental health problems.