The study found that siblings of alcohol-dependent probands reported substantially higher rates for both alcohol dependence and habitual smoking than did the siblings of control probands (Bierut et al. 1998). For example, almost one-half of the brothers and one-fourth of the sisters of alcohol-dependent probands had a lifetime diagnosis of alcohol dependence, rates that significantly exceeded those found in the general population (i.e., among the control sample) (see table 1). Similarly, habitual smoking was more common in the siblings of alcohol-dependent probands compared with the siblings of control probands. Thus, approximately 42 percent of brothers and 30 percent of sisters of alcohol-dependent probands reported habitual smoking, which again was significantly higher than among the siblings of control probands.
