The textbook's pages are yellowed and stuck together in parts, but what I'm looking for isn't hard to find.
Blunted affect can be considered to have 3 components: (1) decrease in facial expression; (2) decrease in expressive gestures and other body language; and (3) decrease in modulation of the volume, pitch, and speed of speaking.
The telephone rings at one in the morning and this is how I know it's him. He tells me plainly that he is drunk, he is driving, it is dark. Almost offhandedly, he adds that he hates everybody, most especially me, and, from his impartial point of view, this existence business leaves a lot to be desired.
"Don't worry," he tells me the next day, almost laughingly. "I'll never do it."
"You said you wanted to overturn your car," I say, and this is true.
There is a brief silence on the other end of the telephone and I strain to listen to the noises of his breathing, slow and even. "If I wanted to veer off of the road," he says, "I would have just done it. I wouldn't have called you."
All I can say, in the smallest voice I have, is, "I thought you wanted me to hear it." And if he were here that would be his cue to pull me against him, hold me in his arms and murmur, "No, no," but, of course, he isn't.
Blunted affect can be found in several disorders other than schizophrenia, including Parkinson's disease, depression, autism, vascular dementia, and multiple system atrophy. In the context of schizophrenia, antipsychotic medications complicate the assessment of blunted affect as they can induce this symptom (although this is much less of a problem with second-generation drugs than with the first generation).
Block quotations courtesy of: T. Kitamura, A. Kahn, R. Kumar (1984)
Reliability of clinical assessment of blunted affect
Acta Psychiatrica Scandinavica 69 (3)