Early illicit drug use and the age of onset of homelessness

We investigate the effect of taking up daily use of cannabis on the onset of homelessness by using Australian data. We use a bivariate simultaneous mixed proportional hazard model to address potential biases due to common unobservable factors and reverse causality. We find that taking up daily use of cannabis substantially increases the probability of transitioning into homelessness for young men but not young women. In contrast, the onset of homelessness increases the probability of taking up daily use of cannabis for young women but not for young men. In a trivariate extension we find that the use of other illicit drugs at least weekly has no additional effect on transitions into homelessness for either gender but there is a large if imprecisely estimated effect of onset of homelessness on taking up weekly use of such drugs for young women