Previous studies have established that a single common factor model adequately describes the abuse and dependence criteria (Krueger et al., 2004; Mewton et al., 2011; Proudfoot et al., 2006). Accordingly, we fit a model with a single latent factor. Model fit was quite good (CFI=0.995; TLI=0.998; RMSEA=0.031). Standardized factor loadings for each of the 11 AA and AD symptoms are included in Table 3. Although the factor loading for LP was strong, it had the lowest loading compared to all the other symptoms. Results presented represent the sexes pooled, as loadings did not qualitatively differ across the sexes (i.e., for both men and women, the factor loading of LP was lower than for any other symptom). A formal test of full measurement invariance indicated that sex differences exist (robust chi square difference test =38.6, df=7, p<0.001), as expected given sex differences in thresholds for each item. Fit indices were nearly identical across the constrained and unconstrained models.
