In this preliminary study, we found that the BNSS had excellent interrater and test–retest reliability as well as strong internal consistency. Its concurrent validity was also supported by its relationship to 2 other widely used negative symptom scales. With regard to discriminant validity, the BNSS did not have a significant relationship with positive symptoms, while the predictive validity was supported by its relationship to a measure of global psychopathology. We also found 2 factors that we interpreted as reflecting the underlying constructs of anhedonia/avolition/asociality and emotional expressivity. Similar factors have been found in other studies of negative symptom rating scales.16
The Distress item did not load onto any of the factors, but this may have been due to restricted variance in that item in the current sample; in a group with greater severity and more variance, the Distress item may load onto one of the other factors. The concept of distress—or as in the BNSS, a lack of normal distress—is not usually considered a negative symptom. However, removing that item did not lead to a meaningful change in the internal consistency of the scale. Measures of distress have also been used in combination with negative rating scale scores to delineate patient groups with and without primary negative symptoms, with good validity (C. Arango, J. Bobes, B. Kirkpatrick, M. Garcia-Garciad, and J. Rejase on behalf of the CLAMORS Study Collaborative Group, unpublished data).18–32
Further study will be needed to determine whether this item can serve this purpose or be useful in other ways. Whether or not this item has utility with regard to delineating deficit and nondeficit groups, a lack of emotionality has long been noted to be a prominent feature in some people with schizophrenia,1
and our results suggest that this feature is related to negative symptoms as usually defined.
The current study did not address some important psychometric characteristics of the BNSS. These include its ability to detect change in clinical trials and its relationship to variables previously shown to be related to negative symptoms, such as neurological signs. Its relationship to the deficit/nondeficit construct (ie, primary, enduring negative symptoms33
) is also unknown, as our small sample did not permit an examination of this issue. The small sample size also raises the question of the stability of the factor structure we found. Another limitation of our study is that all the rating scales were completed by the same rater.
There were also limitations to the generalizability of our findings. Our sample consisted of outpatients whose symptoms were typically mild to moderate. Psychometric properties and the amount of time needed to administer the BNSS may differ in more severely ill groups. However, in light of the relatively restricted variance in our sample, our ability to attain good interrater reliability suggests that reliability in more severely ill groups should also be good. We also did not use information from informants, although in many studies that may be feasible. On the other hand, the good interrater reliability was obtained by raters from 3 different sites and different professional training. We did not find a relationship to our measure of cognitive function; a larger sample or other, more extensive measures might have found such a relationship.
There is increasing sensitivity to the problem of pseudospecificity8,34
or primary vs secondary negative symptoms in the study of psychotic disorders. The intent of the distress item is to aid in this area. The relationship of BNSS total score to depression was not significant, and there was no significant relationship to positive symptom scores. Although our sample size was a limitation, the effect size was small for both of these relationships, so even in a larger sample, there is not likely to be strong correlation. However, in future studies, interpreting BNSS scores in the context of rating scale scores for depression, extrapyramidal symptoms, and psychotic symptoms may be useful. In clinical trials, an appropriate design can also help minimize the problem of pseudospecificity.8
The relative value of the BNSS, compared with the SANS, PANSS negative symptom subscale, the Negative Symptom Assessment, etc., cannot be adequately assessed by any one study. Use of the BNSS in clinical trials in which another negative symptom scale is used would be informative. The potential advantages of the BNSS—which need to be tested—are brevity; a separation of appetitive and consummatory anhedonia, asociality and anhedonia, and behavior and internal experience; a strong theoretical base; the distress item; and its embodying the recommendations of the Consensus Development Conference. Its design enables researchers to consider many aspects of negative symptoms separately and relate them to treatments, imaging, and other variables.
Our multisite study demonstrates that raters from a variety of backgrounds can achieve excellent interrater reliability with relatively brief training. Should the BNSS prove to be sensitive to change, it may also be useful for assessing treatment response and clinical progress in routine clinical care. Other study designs and samples with different clinical features would be helpful in assessing its utility.