Principal and Differential Effects of Haloperidol and Placebo Treatments upon Speech Disfluencies in Stutterers

Fourteen stutterers completed a double-blind crossover study of the effects of Haloperidol and Placebo treatments upon their speech disfluencies. Although clearly not clinically effective, Haloperidol had a statistically significant effect upon reducing disfluency frequency and increasing speaking rate. For most subjects, drug-related reductions in disfluency severity resulted from a decrement in whole-word and phrase repetition, interjection, and revision-type disfluencies rather than from fewer part-word (elemental) repetitions and prolongations of sound or of silence. Neurotic personality profile correlated positively with an overall placebo effect, and there was a positive correlation between abnormal EEG and the drug effect. These findings are discussed in light of the nature of speech disfluency and stuttering and Haloperidol's biochemical and behavioral actions.