studies, low Conscientiousness in childhood predicts cigarette smoking in adulthood [48,49]. Longitudinal studies in Europe also suggest that high scores on Neuroticism and Extraversion during adolescence increase the likelihood of being a smoker later in life [18,50]. A common hypothesis is that individuals with high Neuroticism use drugs to self-medicate [51,52]. Finally, third variables might be responsible for the association of personality and addictive behaviors. For example, personality traits and cigarette smoking are both highly heritable [53,54], and could be influenced by common genetic factors [37].
