use, exclusion of concomitant diseases is not necessarily a requirement for all studies. Concomitant diseases as an experimental factor in study designs can be useful in creating more homogenous groups and reducing heterogeneity (Liu et al., 2004; Liu et al., 2006). Moreover, alcoholics with cirrhosis or other concomitant diseases can represent a more severe subtype and thus enhance the effect size (Liu et al., 2007). For example, comparison of brain gene expression from alcoholics with cirrhosis and those without revealed widespread differences in transcriptome patterns in cirrhotic versus noncirrhotic alcoholics and these differences in gene expression likely contribute to the more severe brain dysfunction observed in cirrhotic alcoholics (Liu et al., 2007). Blood alcohol concentration at the time of death is not currently available for all cases but is an important factor when subdividing cases on the basis of drinking behavior. A record of blood alcohol concentration in human subjects may be relevant considering that alcohol-responsive gene networks depend upon the duration of ethanol consumption in mouse models of excessive drinking (Osterndorff-Kahanek et al., 2015). Furthermore, inclusion criteria should account for variables such as age, ethnicity, developmental disorders, history of other psychiatric or neurological disorders, and other degenerative diseases. Minimizing
