Treatment adherence in Asthma and Attention Deficit Hyperactivity Disorder (ADHD), Personality traits, Beliefs about medication and Illness perception

Adherence to medication in asthma and attention deficit hyperactivity disorder (ADHD) is important because medication may prevent serious consequences, possibly with lifelong effects. Several factors have been identified that influence adherence to medication in these disorders, but the importance of personality traits, beliefs about medication and illness perception has been insufficiently explored. The overall aim of this thesis was to study adherence to medication in asthma and ADHD, and in particular factors associated with adherence. The participants (n=268) in Study I were recruited epidemiologically and consisted of young adults with asthma, aged 22 years (±1 year). Impulsivity and, in men Antagonism and Alexithymia were associated with low adherence among respondents with regular asthma medication (n=109). The participants (n=35) in Study II were recruited from primary care clinics and consisted of adults (mean age 53 years). In men, Neuroticism was associated with low adherence, but Conscientiousness with high adherence. Beliefs about the necessity of medication were positively associated with adherence behaviour in women. In the total sample, a positive necessity-concern differential of beliefs predicted higher adherence. The participants in Study III, IV (n=101) and V (n=99) were recruited from Child and Adolescent Psychiatric clinics and consisted of adolescents with ADHD on long-term ADHD medication. Study IV assessed the reliability and validity of Swedish translations of the Beliefs about Medicines Questionnaire-specific (BMQ-Specific) and Brief Illness Perception Questionnaire (B-IPQ) for use in adolescents with ADHD. Exploratory Principal Component Analysis (PCA) loadings of the BMQ-Specific items confirmed the original components, the specific-necessity and specific-concerns. The exploratory PCA for B-IPQ revealed two components; the first one, B-IPQ Consequences, captured questions regarding perceptions of the implication of having ADHD (items 1, 2, 5, 6 and 8) and the second one, B-IPQ-Control, the perceptions of the ability to manage the ADHD disorder (items 3, 4 and 7). Adherence correlated positively with BMQnecessity-concern differential but negatively with beliefs about medication regarding concerns and side effects as well as Antagonism. Adolescents with more beliefs in the necessity, but with less concerns and side effects were less intentionally non-adherent. Adolescents with more perceptions that ADHD affected life showed less unintentional non-adherence. Negative Affectivity was associated with beliefs in the necessity of medication, but also with concern about medication and side effects. Negative Affectivity was positively associated with perceived consequences in life caused by ADHD and less control over ADHD. Hedonic Capacity was associated with less concerns about medication. In conclusion: In asthma and ADHD, adherence was associated with personality and beliefs about medications treatment. The personality traits showed numerous associations with perception about ADHD and beliefs about asthma and ADHD medication. This thesis increases our understanding of these person-related underlying factors of non-adherence, which may enable targeted actions intended to turn nonadherence into adherence as well as to identify individuals at risk for non-adherence. The Swedish translation of BMQ-Specific and B-IPQ proved to be valid and reliable, suggesting that the scales are useful in clinical work to identify risks of low adherence and to increase knowledge about how adolescents perceive ADHD.