Risk factors for one disorder tend to predispose individuals to other disorders (Kendler et al., 2003; Carr et al., 2013). The high comorbidity of substance and psychiatric disorders (Kessler et al., 1994; Compton et al., 2007; Hasin et al., 2007b) has been conceptualized as forming a meta-structure of broader internalizing and externalizing latent dimensions (Krueger et al., 2002; Kendler et al., 2003; Eaton et al., 2012; Krueger and Markon, 2014). In a US national sample, childhood maltreatment affected the risk for specific adult mood, anxiety, personality, and substance use disorders primarily through the broader internalizing and externalizing dimensions rather than impacting the risk for specific individual psychiatric disorders (Keyes et al., 2012). Further, in another US national sample, familial aggregation of mood, personality, and substance use disorders was explained by underlying vulnerabilities to internalizing and externalizing dimensions transmitted across generations (Kendler et al., 1997). However, up to now, 9/11 research has focused on individual disorders rather than the broader internalizing and externalizing dimensions, leaving unknown whether 9/11 effects are primarily through these domains, whether such effects differ between the internalizing
