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Blindness, Bias, and Validity in a Trial of
Antidepressant Medication for Chronic Tension-Type Headache
Tkachuk G., et al
Posted July 2003  
Presented at: 45th Annual Scientific Meeting American Headache Society June 19-22, 2003; Chicago, Illinois

Objectives: To examine treatment blindness, factors associated with blindness penetration, and subjective biases of neurologists and participants in a clinical trial of antidepressant medication for chronic tension-type headache.

Background: Considerable evidence suggests the ‘blind’ is frequently broken in double-blind trials of antidepressant medication, and their validity has been questioned. Trials in headache have yet to examine the extent to which the blind is broken and issues related to bias and validity.

Conclusions: Neurologists successfully penetrated the blind for both conditions after three months of treatment, while patients did so only in the antidepressant condition. However, we found no evidence that penetration of the blind compromised trial validity. Nonetheless, the integrity of the blind cannot be assumed; it must be assessed.