Changes over time among homeless young people in drug dependency, mental illness and their co-morbidity.

A cross-national survey was conducted among 358 recently homeless young people in Melbourne and Los Angeles. Drug dependence and mental illness were assessed at baseline, 6 and 12 months. At each time point, participants were classified as no condition, drug dependent, having a mental illness or dual condition. Low levels of drug dependence or mental illness or both were reported at each data point. Most young people were classified as neither drug dependent nor having mental illness at baseline and remained so for the 12-month period and few remained drug dependent, or had continuing mental illness or both. Half to two-thirds of young people classified as having one or both conditions were subsequently reclassified as "no condition". There was no evidence of a consistent pathway from either drug dependence or mental illness to co-morbidity. Most young people reported an absence of mental illness and/or drug dependence at each time point. Improvement from one or both conditions at each transition suggests it may be more effective to provide interventions to address drug dependence and mental health problems to young people early in their experience of homelessness.