Ethical considerations arise in studying substance abuse, an illegal behavior often associated with other difficult individual and family pathologies (see also above). Such ethical considerations suggest that it is unlikely that any large, truly population-based sample for dependence on illegal substances will be readily obtained. Sampling research volunteers and examining the extent to which the volunteers’ demographic characteristics match or deviate from those of the larger drug abuser communities provides one approach to this issue. We cannot quantitate the selection biases that might be imposed by factors not reflected in the demographic features (eg gender and self-reported racial/ethnic background) that are often used to characterize subgroups.
