= 0.06, and other substances = 0.09. Since the distribution of age of onset was skewed, medians are more informative than means. Median age of first use was tobacco = 13, alcohol = 14, cannabis = 15, inhalants = 13, and other substance = 15. Rank correlations between the reported age of first use of the different substances based on pair-wise complete data ranged between 0.38 and 0.59.
