Formula method for stimulus setting in bilateral electroconvulsive therapy: relevance of age.

Seizure thresholds were determined by titration in consecutive electroconvulsive therapy (ECT) patients at the first (n = 146) and sixth (N = 83) ECT sessions. Equations to predict the threshold at the first and sixth ECT were computed from these data using a stepwise linear regression model. These equations were tested prospectively at the first ECT (n = 48) and sixth ECT (n = 26) sessions. Stimulus dose derived from the corresponding equations yielded adequate seizure (successful) in 82% and 84% of patients, respectively. Predictions based on age alone (disregarding two other significant variables--illness severity and inion-nasion distance) were estimated at these two ECT sessions. This would not appreciably compromise the success rate. The "formula" method using age alone may therefore be used in routine clinical practice.