ABSTRACT

Our main aim was to estimate the extent of overlapping etiology between caffeine consumption and response and normative and pathological personality. Linear mixed-effects models were used to identify normative personality domains and personality disorder (PD) traits for inclusion in multivariate twin analyses together with individual caffeine related measures. Data were obtained from Norwegian adult twins in a face-to-face interview conducted in 1999-2004 as part of a population-based study of mental health and through self-report in 2010-2011 and 2015-2017. Personality disorder data was available for 2,793 twins, normative personality for 3,889 twins, and caffeine for 3,862 twins (mean age 43.0 years). Normative personality was assessed using the self-reported Big Five Inventory, PD traits were assessed by the Structured Interview for DSM-IV Personality, and caffeine consumption, toxicity, tolerance, and withdrawal were assessed through a self-report questionnaire developed at the Norwegian Institute of Public Health. Caffeine measures were found to be moderately heritable, h2 = 30.1%-45.0%. All normative personality domains and four PD traits, antisocial, borderline, dependent and paranoid, were significantly associated with at least one caffeine variable. A small proportion of variance in caffeine consumption was attributable to genetic factors shared with normative personality (1.3%) and personality disorders (11.4%). A modest proportion of variance in caffeine tolerance and toxicity was attributable to genetic factors shared with both normative personality (26.9%, 24.8%) and personality disorders (21.0%, 36.0%). The present study found caffeine consumption and response to be heritable and provides evidence that a small to-modest proportion of this genetic etiology is shared with both normative and pathological personality.