Kaplan-Meier survival models were used to determine the age of onset for Conduct Disorder, Drug or Alcohol Abuse, Drug or Alcohol Dependence and Major Depressive Disorder using familial risk status as an explanatory variable and tested with a Tarone-Ware statistic (see Figure 1). Survival time was significantly shorter for high risk offspring with “loss of survival” beginning to occur at about age 12. For major depressive disorder, χ2 = 9.12, df =1, P = 0.003; for Drug or Alcohol Abuse, χ2 = 9.98, df =1, P = 0.002; for Alcohol or Drug Dependence χ2 = 5.79, df =1, P = 0.016; and for Conduct Disorder χ2 = 20.12, df =1, P < 0.001. These results indicate that high risk offspring not only have greater incidence of these disorders as shown in Table 5, but also have an earlier onset as well.
