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Asymmetrical Transfer: An Inherent Weakness of Repeated-Measure Drug Experiments

Published online by Cambridge University Press:  29 January 2018

Keith Millar
Keith Millar*
Affiliation:
University Department of Psychiatry, University Hospital and Medical School, Clifton Boulevard, Nottingham NG7 2UH
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Summary

When subjects act as their own controls in drug experiments there is a risk of asymmetrical transfer between treatment conditions, with the result that treatment effects are determined largely by order of administration. In such cases the effect of a drug may be reduced or exaggerated, and prior treatment with a drug may affect placebo conditions. Asymmetrical transfer is probably much more common than is generally realized. Suggested causes include inadequate wash-out between treatments, state-dependent learning, adoption of learning strategies, and practice effects. The problem is illustrated by the re-analysis of a paper on the effects of benzhexol on memory, published recently in this journal (Potamianos and Kellet, 1982). The advantages of separate-group experimental design are reconsidered.

Type
Research Article
Information
The British Journal of Psychiatry , Volume 143 , Issue 5 , November 1983 , pp. 480 - 486
Copyright
Copyright © 1983 The Royal College of Psychiatrists 

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