Evidence for two distinct domains of negative symptoms: Confirming the factorial structure of the CAINS.

Negative symptoms are an important predictor of course of illness as well as social and occupational functioning. Clinically effective interventions are scarce. For negative symptoms to become a reliable primary endpoint in treatment studies, clear operationalization and construct validation is needed. Recent factor analyses mostly find two main factors for negative symptoms: diminished expression und amotivation/anhedonia. The Clinical Assessment Interview for Negative Symptoms (CAINS) consists of the subscales "motivation and pleasure" and "expression". We assessed three samples of subjects with schizophrenia (n = 105) for different aspects of the scale's reliability and validity. A confirmatory factor analysis (CFA) of the CAINS confirmed its two-factorial structure. The subscales had distinct correlational profiles: "Motivation and pleasure" was strongly associated with functional outcome and depression and further with neurocognition, positive symptoms and social cognition. "Expression" seems independent of sources of secondary negative symptoms and neurocognition. We found good internal consistency and interrater agreement. Test-retest reliability (two-week interval) was moderate for the CAINS and its "expression" subscale and low for the "motivation and pleasure" subscale. Our findings indicate that the CAINS differentiates reliably between the two main domains of negative symptoms with some questions remaining concerning the validity of the "motivation and pleasure" subscale.