Subdomains within the negative symptoms of schizophrenia: commentary.

In an accompanying article in this theme issue, Blanchard and Cohen review the evidence on the relationships among negative symptoms and conclude that meaningful subdomains within negative symptoms may exist. Specifically, they suggest that blunted affect and poverty of speech may form one such subdomain, and anhedonia, asociality, and avolition may form another. The authors are appropriately cautious in raising this possibility, and they suggest further studies would be needed before it is confirmed. Should the independence of these 2 factors be confirmed, it would have implications for research on negative symptoms. At the Consensus Development Conference on Negative Symptoms, sponsored by the National Institute of Mental Health and held in Rockville, Maryland, on January 26–27, 2005, one of us (Kirkpatrick) presented a review of the literature on blunted affect. From the starting point of that presentation, a pattern consistent with the existence of separate subdomains similar to those cited by Blanchard and Cohen emerged. We briefly summarize that presentation and discuss some of the issues involved in conducting research on the existence of separate factors within negative symptoms.