Fig. 2: A comparison of long-term cannabis users, long-term tobacco users, and lifelong cannabis/tobacco non-users on age-45 DNA methylation.

The x axis is the mean difference between long-term cannabis users and cannabis/tobacco non-users (Panel A), long-term tobacco users and cannabis/tobacco non-users (Panel B), and long-term cannabis users and long-term tobacco users (Panel C) on the 246 CpG sites at age 45. Mean differences were estimated using robust regression and were adjusted for sex, control probe principal components indexing technical variation, and white blood cell counts. Negative mean differences indicate hypomethylation relative to the comparison group, and positive mean differences indicate hypermethylation. The y-axis is the negative log base 10 p-value, and these were truncated at a value of 100. The dashed vertical line is the reference line that represents no difference in means between groups. Panel A=Long-term Cannabis Users (N = 73) vs. Cannabis/Tobacco Non-users (N = 182). Panel B=Long-term Tobacco Users (N = 56) vs. Cannabis/Tobacco Non-users (N = 182). Panel C=Long-term Cannabis Users (N = 73) vs. Long-term Tobacco Users (N = 56). The colors indicate statistical significance: Blue= p < 0.00020 (significant at Bonferroni-adjusted threshold for 246 tests). Red= p < 0.05. Gray= p ≥ 0.05.