instrumentation so data from different studies can be combined and/or compared, and development of measures that better capture the multi-dimensional nature of dependence and its evolution over time in the individual’s addiction history. Limiting the use of retrospective, self-report data may also help reduce inconsistencies in phenotype outcomes; biomarkers should be incorporated where possible to confirm self-report. In addition, proxy (e.g. sibling or spouse) reports can be used to provide supporting information as medical records rarely comprehensively record substance use and not all dependent subjects seek treatment. Funding agencies and scientific societies should make a major effort to ensure that all large scale studies in drug addiction incorporate a core set of measures that are fully comparable, starting with definitions of use, quantity, frequency as well as aspects of abuse and dependence.
