However, the ultimate goal or purpose of the FFM of personality disorder is not simply to develop an alternative means to reproduce the existing diagnostic categories (Clark, 2007). Future research needs to address whether the FFM succeeds as an alternative to the existing nomenclature. For example, an informative next step would be field trials, within clinical samples, that directly compare the FFM to the DSM with respect to clinical utility, as well as validity (First, 2005). Studies that directly compare the two models with respect to validity (Trull et al., 2003) and utility (Samuel & Widiger, 2006) have been conducted, but research on the application of the FFM within clinical settings is clearly needed. However, even here instrumentation may prove to be problematic.
