One of the biggest challenges of genetic research in addiction is the heterogeneity of the phenotype studied and a lack of consistent measurements for outcomes across studies. For instance, alcoholics vary greatly in their age of onset of problem drinking, alcohol symptoms, drinking history and co-morbid disorders. A number of scales also exist to measure nicotine dependence; the two most commonly used being the Fagerström Test for Nicotine Dependence (FTND) and Diagnostic and Statistical Manual – IV (DSM-IV). However, these two measures correlate only weakly (23), and they are likely capturing different aspects of dependence. The FTND may be a stronger measure of physical dependence, while the DSM-IV emphasizes the awareness of dependence, such as recognition of adverse consequences of smoking, a desire to reduce use, and mood changes that occurs during withdrawal. Thus, there is a need for consistent 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
