Elsevier

Comprehensive Psychiatry

Volume 49, Issue 5, September–October 2008, Pages 460-468
Comprehensive Psychiatry

A study of patients with personality disorder not otherwise specified

https://doi.org/10.1016/j.comppsych.2007.12.008Get rights and content

Abstract

Background

Personality disorder not otherwise specified (PD NOS) is a frequently applied diagnosis, but we lack knowledge of the clinical appearance of patients receiving the diagnosis. This study applied a large clinical sample (N = 1516) to investigate (1) the prevalence and diagnostic and clinical characteristics of patients with PD NOS defined according to Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and (2) the prevalence and psychosocial impairment associated with different definitions of PD NOS.

Method

Patients from the Norwegian Network of Psychotherapeutic Day Hospitals diagnosed in accordance with the LEAD standard (Longitudinal, Expert, All Data) were evaluated on several clinical measures at admission and discharge from short-term treatment.

Results

The DSM-IV PD NOS category was the third most frequent PD diagnosis. Seventeen percent of the total sample and 22% of those with PDs had a PD NOS diagnosis, with an average of 9 PD criteria. Patients with PD NOS were heterogeneous with respect to types of PD criteria, 41% were not subthreshold on any specific PD. The PD NOS patients were intermediate between patients with specific PDs and those with no PD regarding number of fulfilled PD criteria and several social and clinical variables. Alternative operationalizations of PD NOS, that is, subthreshold on at least 2 specific PDs or meeting a minimum of 10 PD criteria, resulted in lower prevalence rates and defined clinically more impaired patients.

Conclusion

The PD NOS defined according to DSM-IV has a high prevalence and seems to capture a group of patients with fewer PD criteria and less severe psychosocial impairment compared to patients with specific PDs. The findings indicate that the operational definition of PD NOS may have a strong impact on the prevalence and clinical appearance of patient receiving this diagnosis.

Introduction

The Diagnostic and Statistical Manual of Mental Disorders (DSM-III) and later revisions of the diagnostic manual [1], [2], [3] have provided explicit criteria for the various types of personality disorder (PD). However, all the diagnostic manuals have included a diagnostic category for PD not otherwise specified (PD NOS) and in this way accounted for the possibility that not all patients may fit into the current diagnostic prototypes represented by the 10 specific PDs. In a meta-analysis of the prevalence and use of DSM-III and DSM-IIIR PD NOS diagnoses, Verheul and Widiger [4] concluded that in structured interview studies, PD NOS was the third most frequently used PD diagnosis, whereas in nonstructured interview studies, PD NOS was often the single most frequently used diagnosis. Even if PD NOS seldom is included in epidemiological studies of PDs, the estimates of PD NOS in the general population, based on a few such structured interview studies, range between 3% and 6%, whereas in clinical samples, the absolute prevalence of PD NOS is estimated to be in the range of 8% to 13% [4], [5], [6], [7], [8]. Verheul and Widiger [4] also reported the relative prevalence of PD NOS (ie, prevalence of PD NOS divided over the overall Axis II prevalence excluding PD NOS), estimated to range from 21% to 49%.

One may ask if the high prevalence of PD NOS indicates a lack of precision of the classification system, and subsequently that more prototypes should be defined, or if it simply reflects the variety and complexity of personality problems seen in clinical practice [9]. A new development in DSM-IV was the introduction of general criteria for PD [3]. To receive a specific PD diagnosis, an individual must both meet the general PD criteria and criteria for a specific PD. As for PD NOS, this category is defined for 2 situations: (1) the individual's personality pattern meets the general criteria for a PD and traits of several different PDs are present, but the criteria for any specific PD are not met (mixed PD) or (2) the individual meets the general PD criteria and is considered to have a PD that is not included in the classification (other PDs, eg, passive-aggressive or depressive PD), the so-called appendix diagnoses. According to the general criteria, a PD is an enduring and deviating pattern of inner experience and behavior that is inflexible and pervasive and leads to clinically significant distress or impairment in social, occupational, or other areas of functioning. The deviating pattern should manifest itself in 2 or more of the following areas: cognition, affectivity, interpersonal functioning, or impulse control. Thus, the current situation is that the DSM-IV manual provides relatively few guidelines with respect to the assessment of the mixed type of PD NOS. Concerning passive-aggressive or depressive PD, the DSM-IV has provided criteria sets for further study. However, in most standard diagnostic structured interviews these criteria are not included. A particular problem is the lack of a good operational definition of the general PD criteria, leaving the evaluation of PD NOS to a large degree to clinical judgment.

Some of the structured diagnostic interviews have included directions for assigning a PD NOS diagnosis, mixed type. In Structured Interview for DSM-IV Personality Disorders (SIDP-IV) [10], PD NOS (mixed type) should be applied when the subject is one criterion below the diagnostic threshold for 2 or more PDs, whereas International Personality Disorder Examination (IPDE) [11] requires the presence of at least 10 criteria from the specific PDs. These directions may be regarded as welcoming attempts at a more precise definition of the disorder but has so far not been included in the DSM. On the other hand, Structured Clinical Interview for DSM-IV Personality Disorders (SCID-II) [12] only requires that the subject meets traits from more than one specific PD, in addition to the general PD criteria. As shown by Verheul and Widiger [4], the assessment methods tend to produce different PD NOS prevalence rates.

The PD NOS has been an overlooked diagnostic category with respect to clinical research. In a general population study, Johnson et al [5] found that adolescents and young adults with PD NOS were as likely as those with cluster A, B, or C PDs to have Axis I disorders and educational, behavioral, or interpersonal problems. In contrast, the multicenter study of Verheul et al [13] found that PD NOS took an intermediate position between cluster A, B, or C PDs and no PD regarding severity of personality pathology, symptoms, and functional impairment. In another clinical study, Karterud et al [14] also found that PD NOS was associated with less severe psychopathology and better treatment response compared to patients with specific PDs. Whereas Johnson et al [5] assigned a PD NOS to subjects who were one criterion below diagnostic threshold for at least 2 specific PDs, the study of Verheul et al [13] applied a cutoff of 10 PD criteria to assign a PD NOS mixed type. In the study of Karterud et al [14], PD NOS was assigned according to the less specific SCID-II requirements. Thus, inconsistent findings may partly be because of different diagnostic practices. However, because of the lack of studies of PD NOS, we do not know to what degree the various diagnostic directions influence the clinical appearance of the patients receiving this diagnosis. Pagan and coworkers [7] have approached the topic from a somewhat different angle and found that a patient had to fulfill at least 10 PD criteria to reach the level of impairment that characterized those with specific PDs. On the other hand, Verheul et al [13] reported that a cutoff of 5 criteria yielded an additional group of PD NOS patients with a similar level of functional impairment as groups defined according to cutoffs of 10 or 15 PD criteria. Thus, there is a need for more studies of the clinical and diagnostic characteristics of PD NOS patients. A comprehensive evaluation of the PD NOS category is of special value as it may further inform issues of cutoff points, subthreshold diagnoses, and severity dimensions of PDs, which are main topics on the PD research agenda for the forthcoming DSM-V[15].

This study investigated patients with PD NOS in a large clinical sample from the Norwegian Network of Psychotherapeutic Day Hospitals. The sample is an extension of the sample included in the study of Karterud et al [14] who reported experiences with day treatment programs for patients with PDs. In the present study, we focused on patients with PD NOS and applied data from admission to and discharge from day treatment. Our first aim was to investigate the diagnostic and clinical characteristics of patients with PD NOS defined according to DSM-IV that is, meeting the general criteria for a PD, not meeting the criteria for any of the 10 specific PDs, and with no further specification regarding number of traits from specific PDs. We explored the prevalence of DSM-IV PD NOS, the distribution of PD criteria, as well as the sociodemographic and clinical characteristics of the patients receiving this diagnosis, comparing them with patients with a single or multiple specific PDs, as well as patients with no PD. The second aim of the study was to explore the prevalence, functional impairment, and symptom distress associated with various definitions of PD NOS.

Section snippets

Setting and assessment

This multisite study included patients from 12 day-treatment units that specialize in the treatment of PDs, offering intensive, short-term day treatment. The units were part of the Norwegian Network of Psychotherapeutic Day Hospitals, and all units complied with the diagnostic and data collection procedures required for membership in the Norwegian Network [16]. Participation in the study was voluntary, and all patients had given informed written consent before inclusion. The study was approved

Prevalence of PD NOS and distribution of PD criteria

Seventeen percent of the patients in the total sample and 22% of those with PD were assigned a PD NOS diagnosis. When defining relative prevalence of PD NOS as the prevalence of PD NOS divided over the number of patients with at least one specific PD excluding PD NOS, the relative prevalence of PD NOS was 28%. The PD NOS was the third most frequently applied PD diagnosis, after avoidant PD (37%) and borderline PD (26%) (see Table 1).

Defining subthreshold PD as fulfilling one criterion below

Discussion

The PD NOS was the third most frequently applied PD diagnosis, which is in concordance with the findings from the meta-analysis of Verheul and Widiger [4] focusing on DSM-III or DSM-IIIR diagnoses. The absolute prevalence of PD NOS was 17%, matching the prevalence of 16% found in a study from an outpatient clinic for psychoanalysis and psychotherapy that also applied the SCID-II for the assessment of DSM-IV diagnoses [23] but somewhat lower than the prevalence of 22% found in psychotherapy

Acknowledgment

This study was funded by Ullevål University Hospital. We wish to thank the patients and staff from the following day units in the Norwegian Network of Psychotherapeutic Day Hospitals for their contribution to this study: Department for Personality Psychiatry, Ullevål University Hospital, Oslo, Norway; Day Treatment Unit, Lillestrømklinikken, Akershus University Hospital, Lørenskog, Norway; Unit for Group Therapy, District Psychiatric Center, Lovisenlund, Sørlandet Hospital HF, Kristiansand,

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