ALC and NIC are complex conditions to study, given the requirement for ingestion of a psychoactive substance and cohort effects due to temporal and geographic variation in the availability of ethanol and nicotine. Many investigators focus on ALC and NIC, which are clinically salient but multi-component syndromes. 91 As part of the TAG consortium, 92 we determined that the components of the Fagerstrom Test for Nicotine Dependence (a measure of NIC) had heritabilities ranging from relatively high to near zero with important common environmental effects. Other investigators evaluated self-reported lifetime maximum use of ethanol (grams/day) or nicotine (cigarettes per day), and such continuous measures of consumption are often available for secondary analysis of samples studied for other diseases.
