Critical flicker frequency (CFF) and psychotropic drugs in normal human subjects-a review.

This literature review presents summary methodological and statistical data on 33 studies in which critical flicker frequency (CFF) thresholds were used to evaluate the effects of acute oral doses of single psychotropic drugs in normal human subjects. In all, 96 drug-dose-study combinations are represented. CFF was found to be altered to a statistically significant degree (P is less than 0.05) in 51 (65%) of the 79 instances in which inferential statistical methods were used to evaluate the results. As expected, stimulants increased CFF while hypnotics decreased it. There is also a discussion of important methodological considerations in the design of psychopharmacological studies employing CFF. While many studies have shown CFF to be sensitive to the effects of psychotropic drugs, there have not always been adequate controls for extraneous factors (especially, set and suggestion, changes in pupillary diameter, and the presence of other commonly used drugs). Finally, consideration is given to the attempts to increase the sensitivity of the CFF test to drug effects.