Manifestations of personality impairment severity: comorbidity, course/prognosis, psychosocial dysfunction, and ‘borderline’ personality features Lee Anna Clark 1 , Hallie Nuzum 1 and Eunyoe Ro 2 Impairment in personality functioning (briefly, personality impairment) is the core pathology in personality disorder (PD) and an essential indicator of PD-severity. It also is a difficult construct to define and assess. We argue that personality- impairment severity is a latent construct that can be modeled with four indicators: within-PD comorbidity, problematic course/prognosis of both PD and comorbid clinical syndromes, PD-associated psychosocial dysfunction, and features of DSM-5-II borderline PD (BPD). Our literature review documents interrelations among the first three indicators, and studies of PD structure reveal a higher order factor of general PD severity marked most strongly by BPD features. Together, these findings indicate that BPD features may be helpful in the important tasks of defining and assessing personality- impairment severity. Addresses 1 University of Notre Dame, USA 2 Southern Illinois University Edwardsville, USA Corresponding author: Clark, Lee Anna (la.clark@nd.edu) Current Opinion in Psychology 2018, 21:117–121 This review comes from a themed issue on Personality disorders Edited by Carla Sharp and Aidan Wright https://doi.org/10.1016/j.copsyc.2017.12.004 2352-250/ã 2017 Published by Elsevier Ltd. Impairment in personality functioning (or briefly, person- ality impairment) is the core pathology in personality disorder (PD) and essential indicator of PD-severity. It also is an elusive construct to define and measure. Yet, it is a primary criterion in both the DSM-5 [1] alternative model of PD (AMPD) and the ICD-11 PD proposal [2  ]. In the AMPD, a second main criterion is one or more pathological traits, whereas in the ICD-11 proposal, traits are optional specifiers, largely due to differences in the primary purposes of the two classification systems [3  ]. Not unexpectedly, some PD researchers and clin- icians have concerns about diagnosing PD solely on the basis of the elusive construct of personality impairment and for many, even having the additional requirement of pathological traits is not entirely satisfactory. We under- stand the comfort of the relative clarity and familiarity of the main (Section II) DSM-5 [1] (DSM-5-II) criteria, despite the multiple, well-documented limitations of that classification system [4]. In this essay, we argue that PD comorbidity, problematic course/prognosis of PD and comorbid clinical syndromes, psychosocial dysfunction and, perhaps surprisingly, DSM- 5-II borderline PD (BPD) features are all indicators (i.e., not components per se) of the latent construct of PD/ personality impairment severity. As such, these indicators can help to guide definition and refinement of the construct. Comorbidity Comorbidity — co-occurrence of two putatively distinct disorders — is a concern across all of psychopathology [3  ], but for PD, it exposes two fatal nosological flaws: Most individuals diagnosed with PD meet criteria for either (a) two or more PDs (50%)[4,5], yet they have only one personality, indicating invalid categorical struc- ture; or (b) none of DSM’s specific PDs (M = 34%) [6], indicating poor nosological coverage. Thus, no more than 16% of individuals with PD meet criteria for only one type. Consequently, although considerable research-based information has accrued from studies focused on specific DSM-5-II PDs, interpreting these findings is problematic due to rampant comorbidity, which is rarely controlled in such studies. However, this confound is almost universally ignored and findings are interpreted as if they were rele- vant only to the target PD. This is clearly unwarranted and should be eschewed by reviewers and editors, not to mention researchers themselves. Moreover, almost no research has focused on the one-third of individuals with PD who do not meet criteria for any specific disorder, so we actually know much less about PD in general than the total amount of research would suggest. Within-PD comorbidity and PD-severity Within-PD comorbidity is rampant, such that every PD diagnosis has some degree of comorbidity with nearly every other [7]; moreover, when PD diagnoses are scored dimensionally, virtually all correlations among them are positive [8,9,10]. However, this comorbidity is not ran- dom, and a meta-analysis of 33 factor-analytic studies of PD structure [11] in various formats (e.g., both PD criteria and diagnoses) plus PD — five-factor model (FFM) of Available online at www.sciencedirect.com ScienceDirect www.sciencedirect.com Current Opinion in Psychology 2018, 21:117–121