Schöbi, Dominik Esslinger, Jacqueline 2020 Attention-Deficit/Hyperactivity Disorder (ADHD) is highly prevalent in children and adolescents worldwide. Typical symptoms include inattention, impulsivity and hyperactivity. Comorbidity with other disorders, such as Oppositional-Defiant Disorder (ODD) or Conduct Disorder (CD) are very common. Due to child symptoms, families of children with ADHD are prone to impaired family functioning. This includes strained parent-child relationships, higher conflict, more negative emotional experiences and less positive family interactions (Johnston & Mash, 2001; Whalen et al., 2011). Based on the conjecture of physiological under-arousal in children with ADHD (Barkley, 1997), the physiology of individuals with ADHD became a biopsychological research interest. The most frequently investigated biomarker is cortisol, an end product of the Hypothalamus- Pituitary-Adrenal (HPA)-axis, and a principal actor in the bodily stress response. Results regarding diurnal HPA-axis functioning in children with ADHD are largely inconsistent. While some found an effect of ADHD on diurnal cortisol, an equally large body of research did not replicate the claimed difference to non-affected individuals. Again others suggest that differences in HPA-axis functioning are solely related to disruptive comorbid symptoms. HPA-axis functioning is health-relevant and calibrated throughout childhood and adolescence (Boyce & Ellis, 2005; Del Giudice et al., 2011). The axis reacts to everyday experiences (Belsky & Pluess, 2009) and the present thesis aims to inquire, how child symptoms as well as family interactions are connected to cortisol expression. This thesis contributes to understanding two - potentially interacting - determinants of child development and later physical and mental health: The parent-child relationship and the physiological stress regulation in children with ADHD. This was realized through three empirical contributions, based on an intensive saliva and diary sampling design with N= 145 children (n= 65 with ADHD) between 7 and 16 years of age and their parents. Five diurnal saliva samples were collected over seven days. Using a smartphone application, children and one of their parents answered momentary assessment questions three times a day. This allowed capturing family interactions, displayed behavior and positive and negative affect as well as child symptoms. Study 1 set out to determine whether children with symptoms of ADHD or rather, disruptive behavior such as ODD/CD showed a distinct output of diurnal salivary cortisol compared to non-affected peers. Therefore, the cortisol awakening response (CAR) as well as total output across the day via area under the curve (AUC) were derived for children with ADHD, children with symptoms of ODD/CD and a comparison group. Neither ADHD nor ODD/CD symptoms were associated with diurnal cortisol expression. Cortisol was significantly related to child age and stage of puberty, corroborating the importance of developmental-specific covariates in salivary bioscience with children and adolescents. Study 2 focused on everyday interactions between children and their parents to examine the relationship between child symptoms, positive and negative parent behavior and positive and negative affect of children and parents. Child symptoms significantly predicted more negative as well as less positive parent behavior towards the child in all models. Negative parent behavior also predicted higher parent negative affect, emphasizing the impact of children’s behavioral symptoms on healthy family relationships. Study 3 was designed to test whether everyday experiences in the parent-child relationship would be associated with HPA-axis responses. This assessment of natural interactions in everyday family environments as well as child symptoms and diurnal cortisol found some of children’s ADHD and comorbidity symptoms to predict cortisol. In summary, the results suggest that children and adolescents with ADHD or comorbid disruptive symptoms do not differ from comparison children in regards to diurnal cortisol. However, the investigation of cortisol sampled concurrently to the assessment of psychosocial events, showed that children’s symptoms were related to their HPA-axis output. Child symptoms’ impact on family dynamics became especially apparent in the association with more negative and less positive parent behavior towards the child. Family interactions and parent behavior are an important target for prevention, intervention and therapy. Enabling positive and affectionate family relationships is crucial to healthy child development, particularly in the presence of ADHD and comorbid impairments. As parents of children with ADHD and comorbidities face more challenges, families should be provided with the necessary skills to evade vicious cycles where children and parents reinforce one another’s dysfunctional behavior. Interactions of everyday family life are key to our understanding of HPA-axis adaptation to the environment and stress-health links in children and later adults. application/pdf https://folia.unifr.ch/global/documents/309082 https://folia.unifr.ch/documents/309082/files/EsslingerJ.pdf eng info:eu-repo/semantics/altIdentifier/urn/urn:nbn:ch:rero-002-119061 info:eu-repo/semantics/openAccess License undefined info:eu-repo/classification/udc/159.9 Family interactions and cortisol expression in children with attention-deficit/hyperactivity disorder http://purl.org/coar/resource_type/c_db06