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The biomarker cortisol assesses the impact of biopsychosocial stressors that activate the stress response system. Hair has emerged as a valid and non-invasive means of gauging cumulative cortisol deposited over month-long periods of time. Established protocols for the extraction of hair cortisol are being validated and refined in humans, yet methodological information about hair characteristics on cortisol remains limited. In addition to external hair exposures (e.g. dye, time spent outside), we examined hair categorization or type (e.g. kinky, straight) by extending a hair typing methodology for scientific use that is currently popular among hair care professionals. We then examined the interaction between hair type and race on cortisol levels with a hair questionnaire. Three studies were pooled to investigate how sample weight, hair type, race, heat exposures, and hair treatments impacted cumulative hair cortisol concentrations. Study 1 consisted of Adult Kenyan Medical Workers (N = 44); Study 2 Mexican and Mexican Americans (N = 106); and Study 3 American Youth (N = 107). We found significantly higher cortisol in 5 mg of hair when compared to larger sample weights, and higher cortisol in those who spent more time outdoors. Cortisol concentrations differed between racial groups and varied by hair type; moreover, there were directional differences in cumulative cortisol from straighter to curlier hair types which depended on racial group. In addition to demonstrating the impact of relatively novel control factors like hair sample weight, outdoor exposure, and hair type, the present study illustrates the importance of disentangling hair type and race to understand variability in cumulative hair cortisol. These influences should be included in future studies that measure hair cortisol.

Policing inequities are harmful sources of systemic racism perpetuated disproportionately against Black Americans. This includes unjust police encounters in Black communities such as racial profiling, stop-and-frisk, hyperpolicing, aggressive policing, police brutality, and police shootings. A knowledge gap exists in how this mistreatment, via direct or intergenerational exposure, impacts physiological systems in Black youth. Using three studies, we tested how exposure to unjust policing biologically "gets under the skin" of Black youth from infancy to emerging adulthood. Study 1 (IDS) examined associations between neighborhood stop-and-frisk rates and telomere length in infants. Study 2 (NSPAC) explored associations between mothers' experience of unfair treatment by police and developmental and stress related hormone coupling in their children ages 5-15. Study 3 (SDRG) tested whether encounters with police in the 8th grade had a lasting impact on diurnal and waking cortisol six years later during emerging adulthood. Rates of neighborhood stop-and-frisk were associated with shorter telomeres in infants (study 1, IDS). Children whose mothers experienced unfair treatment from police showed, during the TSST, blunted cortisol stress reactivity, slower cortisol recovery, and altered cortisol-testosterone coupling (study 2, NSPAC). Adolescents who experienced police encounters had higher waking cortisol as emerging adults (study 3, SDRG). Policing inequities were linked to biological markers of stress and health across all developmental stages of Black youth. Direct, within child's neighborhoods and intergenerational unjust policing were associated with stress-responsive biological pathways in Black youth. Findings represent a critical and modifiable target when seeking to address persistent racial inequity. [ABSTRACT FROM AUTHOR]