- Age at least 18 years. Rationale: Children under 18 will not be included because many of the measures to be administered in this study are not validated for use with children. Furthermore, the research question under investigation is the drug trajectories of adults, over the age of 18. However, there is no intervention in this study that is contraindicated for older adults, and given that addiction in the elderly is understudied, it is important to include elderly individuals.