IQ and personality traits assessed in childhood as predictors of drinking and smoking behaviour in middle-aged adults: a 24-year follow-up study

Aims. The identification of childhood personality predictors of drinking and smoking behaviour in adults. Design. A 24-year follow-up study. Setting. Prague, the Czech Republic. Participants. Combined cohorts of 220 males and females born of unwanted pregnancies, and 220 control subjects, examined with low attrition rates at ages 9-10, 21-23, 28-31 and 32-35. Measurements. In childhood IQ was assessed by the Wechsler Intelligence Scale, Children (WISC), and personality characteristics were rated by teachers, mothers and classmates. In adulthood questionnaires and face-to-face interviews were used to assess drinking and smoking. Findings. Unwanted pregnancy was not related to adult drinking and smoking. The ratings of childhood personality characteristics were condensed into three personality dimensions, i.e. conscientiousness, extroversion and neuroticism, interpreted as three of the Big Five personality dimensions, and found to show some stability into adulthood. Gender, IQ and the three childhood personality traits were used as predictors of adult drinking and smoking behaviour. Adult drinking behaviour was significantly predicted by the block of the three childhood personality traits, low conscientiousness predicting high drinking quantity per occasion (and heavy episodic drinking) whereas extroversion predicted subjects' average daily consumption. Smoking in adulthood was predicted by low IQ and low conscientiousness. Conclusions. IQ and personality traits in children explain to some degree the drinking and smoking behaviour of adult men and women, but the roles of the different components vary according to the form of substance use.