(BSI) in psychiatric outpatients with intellectual disabilities

Background Diagnostics and care for people with intellectual disabilities and psychiatric disorders need to be improved. This can be done by using assessment instruments to routinely measure the nature and severity of psychiatric symptoms. Up until now, in the Netherlands, assessment measures are seldom used in the psychiatric care for this population. The objective of the present paper is to evaluate the use of the BSI, a widely used standardised questionnaire in general psychiatry, in a well-defined sample of people with borderline intellectual functioning (BIF) or mild intellectual disabilities (ID) diagnosed with one or more psychiatric disorders. Method A total of 224 psychiatric outpatients with either BIF or mild ID participated in this study. All participants were new patients of the two Centres for Psychiatry and Intellectual Disability (CPID) of Rivierduinen, a large regional mental health care provider in the Netherlands, in the period between April 1 2008 and October 1 2009. All participants were assessed by a multidisciplinary team. DSM-IV-TR criteria were applied. The mean total intelligence coefficient (TIQ) was measured with the Wechsler Adult Intelligence Scale (WAIS-III). The BSI was administered in an assisted fashion. Psychometric properties of the BSI were investigated. Bivariate correlations between the subscales were computed to assess differentiation between the scales and mean subscale scores were compared between different DSM-IV-TR subgroups to investigate the discriminant abilities of the scales. A confirmatory factor analysis was conducted. Results The results suggest that the BSI is practically useful. Internal consistencies ranged from 0.70 – 0.96 and thus are considered good to adequate. Subscale intercorrelations showed there is a degree of differentiation between the subscales. Discriminant validity was shown for the subscales Depression, Anxiety and Phobic anxiety. Confirmatory factor analysis showed that de underlying structure of the BSI could be described by the same 9-factor model as reported in previous studies. Conclusions As a result of the psychometric properties illustrated, this study supports the use of the BSI as a screener for psychopathology and a general outcome measure in people with intellectual disabilities. Chapter 5 Utility of the BSI in psychiatric outpatients with intellectual disabilities 53 Introduction It is commonly known by now that people with intellectual disabilities (ID) experience the full range of psychiatric disorders. And even though prevalence rates vary, in most studies, they turn out much higher than in the general population.1–8 In contrast, psychiatric diagnoses are often missed and little is known about the effectiveness of treatment of psychiatric disorders in this population.4,7,9 Therefore diagnostics and care for people with ID and psychiatric disorders need to be improved. This can be done by using assessment instruments to routinely measure the nature and severity of psychiatric symptoms. In the Netherlands, assessment measures are seldom used in the psychiatric care for this population. This is at least in part due to the lack of adequately translated and tested assessment instruments in the Dutch language. In the Dutch language there are only a few measures available specially developed for people with ID and little is known about the utility of existing ‘regular’ assessment measures. This is especially true for self-report measures. Using self–report measures may present challenges due to language and memory problems, a reduced ability to conceptualize and express emotions, as well as due to social desirability.7,10 However, people with borderline intellectual functioning (BIF) or mild ID are generally quite capable of reporting about their own behaviours and feelings.11–15 If self-report measures are used, they are usually developed or modified for people with ID, but with little attention paid to psychometric properties and comparability with existing psychiatric ratings.16 One could argue, as did Kellett et al.,17 that it is ethically and theoretically more appropriate to explore the application of existing non-altered assessment measures before modifying existing, or developing new instruments. Examples of existing self-report measures from general psychiatry already researched for their use in people with ID are the Beck Depression Inventory and the Zung SelfRating Depression Scale,18 the Beck Anxiety Inventory,19 the Zung Self-Rating Anxiety Scale,12 and the Hospital Anxiety and Depression Scale.20 Although more research is needed, all authors stress the applicability and potential utility of these instruments in people with ID. Kellett et al.21,22 evaluated the use of the Brief Symptom Inventory (BSI), a widely used assessment measure in the general psychiatry, in people with ID in the United Kingdom. Their first study consisted of 200 mild ID participants from three distinct groups: a clinical, a community and a forensic group. The second study consisted of 335 participants, all diagnosed with mild ID, but with no reference of psychopathology. Kellett et al.21,22 found that people with ID respond to most questions of the BSI in a similar way as do people without ID and that internal consistency of the different subscales was satisfactory. Moreover they concluded, in their first study, that the BSI 54 Psychopathology in borderline intellectual functioning could effectively discriminate between the different groups. They concluded that the BSI can be employed as an assessment instrument and as a treatment outcome measure in people with ID. The objective of the present paper was to further extend the research on the utility of the BSI in a well-defined sample of people with BIF or mild ID. In view of the findings of Kellett et al.21,22 it is reasonable to hypothesize that the BSI has adequate psychometric properties and can be used in this population.