A novel element of this study is that the variable selection used to generate clusters was guided by the heritability estimate for major features of opioid use related behaviors. Inclusion of the opioid withdrawal symptoms with a higher estimated heritability increased the heritability estimates of opioid use subtypes over those obtained previously by us using a similar approach. Extensions of this method can be used to examine other opioid-related measures or other disorders to yield a comprehensive set of informative and essential phenotypic features.
