Variation in reported rates of child psychiatric disorders in children of AD parents has been noted (Kuperman et al., 1999). Among the factors influencing reported rates are the presence of comorbid psychiatric illness in the AD parent, variation in sample origin (treated versus untreated), and use of relatively small samples. The ascertainment schema used (multiplex versus random samples of unselected alcoholics) may also be an important source of variation. Recent reports from the Collaborative Study on the Genetics of Alcoholism (COGA) study (Kuperman et al., 1999; Ohannessian et al., 2004) and those from our samples (Hill and Muka, 1996; Hill et al 1999a) are based on offspring from multiplex families. Offspring from unselected families of alcohol dependent parents can be expected to have fewer AD relatives and may have a less severe form of the disorder.
