As noted in Table 3, the ns and the ORs for the groups were as follows: non/low tobacco users and non/low marijuana selleck products users (n = 257, OR = 10.1; p < .001), chronic tobacco users and maturing-out marijuana users (n = 15, OR = 5.6; p < .001), late onset tobacco users and late onset marijuana users (n = 30, OR = 3.5; p < .001), and chronic tobacco users and chronic marijuana users (n = 16, OR = 4.8; p < .01). More than 66% of participants were in a comorbid trajectory pair with most in the non/low tobacco use and non/low marijuana use trajectory pair. Correlates of comorbidity Table 3 shows ORs when a single risk variable was controlled. The ORs of the comorbidity of the pairs of trajectories of tobacco and marijuana use were reduced with control on many of the psychosocial risk variables.

For the non/low tobacco use and non/low marijuana use trajectory pair, no single risk factor reduced the OR below 7.2 (OR reduced from 10.1 to 7.2, t = 3.0, p < .01). For the non/low tobacco use and non/low marijuana use trajectory pair, the greatest reduction was obtained by controlling for Delinquency. For each of the four comorbid trajectory pairs, controlling for Peer Marijuana Use generated the largest or next largest reduction in OR. The chronic tobacco use and chronic marijuana use trajectory pair controlling for Peer Tobacco use had the largest reduction in OR. For the chronic tobacco use and chronic marijuana use trajectory group, all of the psychosocial risk variables except the demographic variables (i.e., Gender and Ethnicity) significantly reduced the ORs (see Table 3).

Table 4 presents the results of six sets of multivariate logistic regression analyses (one for each row of the table) for the four selected pairs of tobacco and marijuana use trajectory groups (see Table 4). The leftmost column specifies the variables controlled for. As shown in Table 4, for the non/low tobacco use and non/low marijuana use trajectory pair, which included more than 50% of the sample, no set of risk factors reduced the OR below 6.6. Controlling for the set of externalizing personality attributes produced the greatest reduction in OR for the non/low tobacco use and non/low marijuana use trajectory pair and the late onset tobacco use and late onset marijuana use trajectory pair. It also reduced the OR significantly for the other pairs.

Controlling for the set of peer variables had the greatest reduction in OR for the chronic tobacco use and maturing-out marijuana use trajectory pair and the chronic tobacco use and chronic marijuana use trajectory pair. Controlling for the internalizing personality attributes AV-951 significantly reduced the OR only for the chronic tobacco use and chronic marijuana use trajectory pair. Controlling for all the variables at once significantly reduced the OR for each of the four comorbid trajectory pairs.