Early illicit drug use and the age of onset of homelessness

We investigate the effect of taking up daily cannabis use on the onset of homelessness 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 cannabis use substantially increases the probability of transition into homelessness for young men but not young women. In contrast, homelessness onset increases the probability of taking up daily cannabis use 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 impact of homelessness onset on taking up weekly use of such drugs for young women