["Addiction, EarlyView. ", "\nAbstract\n\nBackground and aims\nPersonality traits have been consistently linked to alcohol use. High neuroticism and extraversion and low agreeableness and conscientiousness are known risk factors for both alcohol use frequency and problematic use across the lifespan. These associations have mostly been studied in the sufficient causality domain (“if X, then probably Y”), whereas little is known about these relationships in the necessary causality one (“if not X, then not Y”). Knowing that a variable is a necessary cause for an outcome helps identify who will be at risk for the outcome and who will be virtually immune. The aim of this study was to test whether personality traits in childhood, adolescence and emerging adulthood might serve as necessary conditions for problematic alcohol use in adulthood.\n\n\nDesign\nThe study is part of the “Flemish Study on Parenting, Personality, and Development”, and it is a 23‐year longitudinal study across four time points [childhood (T1), adolescence (T2), emerging adulthood (T3), adulthood (T4)].\n\n\nSetting\nFlanders (Belgium).\n\n\nParticipants\nAt T1, the total sample consisted of 306 participants (age = 7.8 ± 1.13 years, and 59.15% females), at T2 of 289 participants (age = 15.78 ± 1.16 years, 59.86% females), at T3 of 290 participants (age = 21.78 ± 1.15 years, 59.66% females) and at T4 of 306 participants (age = 30.08 ± 1.13 years, 59.15% females).\n\n\nMeasurements\nPersonality traits were assessed in childhood, adolescence and emerging adulthood using the Hierarchical Personality Inventory for Children (HiPIC) and were related to problematic alcohol use, measured through the Alcohol Use Disorders Identification Test (AUDIT), in adulthood. Necessary Condition Analysis (NCA) was used to test whether specific traits were necessary for the outcome, and to what extent.\n\n\nFindings\nConscientiousness emerged as a developmentally stable necessary condition for problematic alcohol use in adulthood (childhood: d = 0.31, P = 0.050; adolescence: d = 0.33, P = 0.052; emerging adulthood: d = 0.33, P = 0.023; all large effects). No other personality traits reached statistical significance.\n\n\nConclusions\nIt is possible to identify, already in childhood and through the lifespan, personality characteristics that distinguish individuals vulnerable to developing problematic alcohol use in adulthood from those who are not. Specifically, lower levels of conscientiousness appear to be necessary to be at risk of potentially developing problematic alcohol use in adulthood, whereas high levels of conscientiousness appear to lead to virtual immunity.\n\n"]