The largest distinctions in terms of number and severity of symptoms were evinced by Classes 1 and 4. Interestingly, these two groups represented individuals with very similar demographic traits, with roughly equivalent proportions of males (44% in Class 1 versus 49% in Class 4) and females (55% in Class 1 versus 50% in Class 4). Both classes were also majority White and had experienced uniformly high levels of non-assaultive trauma (though exposure to some kind of trauma, broadly defined, was a criterion for inclusion in the study). However, membership in Class 4 was also characterized by very high levels of physical (26% versus 60%) and sexual (9% in Class 1 versus 34% in Class 4) assault. Physical and sexual assault rates were highest in Class 4 and lowest in Class 1 compared to all groups. Class 4 members had also initiated drinking behaviors earlier than members in other classes, at 13 years and 9 months. By contrast, Class 1 members reported the lowest mean age of first drink, at 16 and a half. The rate of both parents having AUD was over twice as high in Class 4 than in Class 1.
