several laboratories (Pandey, Fawcett, Gibbons, Clark, and Davis, 1988; Tabakoff et al., 1988). MAO is an enzyme that is important in the metabolism of a variety of brain neurotransmitters that affect behavior, including dopamine, norepinephrine, epinephrine, and serotonin.
Decreased Sensitivity. Studies of individuals at high risk for alcohol abuse and dependence have also used challenge paradigms in which responses are measured to both placebos and ethanol. Results from some investigations (Moss, Yao, and Maddock, 1989; Lex, Lukas, Greenwald, and Mendelson, 1988; Savoie, Emory, and Moddy-Thomas, 1988; O'Malley and Maisto, 1985) suggest that in general these high-risk individuals may be less sensitive to the effects of alcohol than controls. They have less intense subjective feelings of intoxication following modest doses of alcohol (Schuckit, 1992). This is seen in such diverse measures as body sway, blood alcohol levels, and cortisol release following challenge. This again suggests that a genetic factor that decreases sensitivity to alcohol may play a role in the development of the illness. Schuckit (in press, 1994) has recently demonstrated that a low level of response to alcohol at age 20 was associated with a fourfold increased likelihood of future alcoholism in both sons of alcoholics and sons of controls.
Cognitive and Motor Functioning. There is some research that indicates that cognitive impairments are present in some children of alcoholic parents (Drejer, Theilgaard, Teasdale, Schulsinger, and Goodwin, 1985; Knop, Teasdale, and Schulsinger, 1985; Schaeffer, Parsons, and Yohman, 1984; Tarter, Hegedus, and Gaveler, 1984; Gabrielli and Mednick, 1983). The impairments are in lower verbal intelligence quotients, lower levels of reading comprehension, and problems with logic and abstract reasoning in achievement tests. These results have not been widely replicated. Some studies have found few differences on these measures when children of alcoholics are compared with controls (Drake and Valliant, 1988; Schuckit, Butters, Lyn, and Irwin, 1987), and the results that are found may pertain only to subgroups of children with multiple risk factors, such as those whose mothers had high-risk pregnancies and those with fetal alcohol effects.
The majority of studies on psychosocial risk factors focus on adolescent onset. Many of the studies focus on the risk of initiating use, whereas the risk of escalating to abuse or heavy use has received less attention. Unfortunately, much of the work done in this area is cross-