Twin studies provide a method for examining the genetic relationship between different measures of alcohol use and problems. While some twin studies indicate that the genetic correlation between measures of regular alcohol consumption and problems is strong (Grant et al., 2009; Kendler et al., 2010), there is also evidence that there are genetic risk factors unique to alcohol problems (Dick et al. 2011). Additionally, recent twin studies examining the genetic relationship between the DSM-IV alcohol dependence criteria have indicated that the seven items are not genetically homogeneous (Kendler et al, 2011). Therefore, different measures of alcohol use and problems may be mediated by different genetic factors. This has implications for gene identification studies in that there are valid reasons why true genetic findings may not replicate across studies that have assessed different aspects of alcohol use and dependence.
