Children’s early life experiences cause the emergence of individual differences in stress coping and social behavior. Attachment styles (AS) conceptualize stable behavioral patterns in response to...Show moreChildren’s early life experiences cause the emergence of individual differences in stress coping and social behavior. Attachment styles (AS) conceptualize stable behavioral patterns in response to stress and can predict long-term susceptibility to mental illness. This study investigates the relationship between 1-year-old infants’ AS, their hormonal stress response in terms of cortisol reactivity (CR) - both assessed in the course of the Strange Situation procedure - and the influence of these factors on children’s scores on the Child Behavior Checklist’s internalizing behavior problem scale (CBCL-I) five years later. Based on previous research, CR was expected to be higher with insecure compared to secure AS. Insecure AS and higher CR in infancy were expected to be associated with higher CBCL-I scores in later childhood. CR was hypothesized to partly mediate the relationship between AS and CBCL-I. Relevant longitudinal data (n=220; 40.8% female, 51.7% male) were drawn from a sample of mother-child dyads (“BIBO” research project). No evidence for any of the hypotheses could be found, as the analyses yielded no statistically significant associations between AS and CBCL-I scores, AS and CR, or CR and CBCL-I. Consequently, testing for CR’s potential mediating role was deemed irrelevant. The results contradict previous findings and raise important questions. The study’s limitations are discussed and suggestions are derived to inform future research on stress pathways in the pathogenesis of mental disorder. Above all, the poorly understood role of potentially decisive covariates in the interplay between AS, CR, and internalizing behavior need to be investigated more thoroughly.Show less