Preliminary data suggest the possibility of linkage between the alpha-haptoglobin locus and third component of complement locus and depression spectrum disease, a depression which is familially defined by the presence of alcoholism in the first-degree family member.
The differences between FHP and FHN groups on correlations between DBH and peak intoxication or usual drinking history raise speculations that the "normal" (FHN) relationship between alcohol intake and plasma DBH activity may be impaired in individuals at high risk (FHP) for the future development of alcoholism.
These results are consistent with an effect of a moderate dose of ethanol on PRL levels and further characterize differences in reactions to ethanol for men at higher and lower risk for the future development of alcoholism.
Various types of phenotypic markers are discussed and alcoholism is taken as a model for a more detailed discussion of available putative phenotypic markers and of research strategies to be used, namely the pharmacological challenge in high risk subjects (e.g. ethanol and TRH challenge).