The findings of this study should be interpreted in light of several limitations. First, as in previous studies of probability of treatment-seeking (Wang et al., 2004; Olfson et al., 2012), information about health insurance coverage, income, and geographic location for each year of the person’s life was not available. Second, we examined patterns of treatment-seeking among all individuals with SUD. Because many individuals achieve remission without accessing treatment (Blanco et al., 2013c; Lopez-Quintero et al., 2011), it is possible that some individuals with SUD may not require treatment, although recent data suggest that treatment for SUD increases the probability of remission and decreases the probability of new onset of other SUDs (Blanco et al., 2014a). There is a need to systematically examine how to most appropriately define objective need for the treatment. Third, information on some potentially important determinants of help-seeking, such as local availability of SUD treatment services (Cummings et al., 2014), was not available. Fourth, we based our analyses in DSM-IV categories. Recent work proposes cross-walks between DSM-IV and DSM-5 disorders and suggests different potential thresholds (Compton et
