OBJECTIVE Electroconvulsive therapy (ECT) is performed under anesthesia and muscle relaxation. Only well-generalized seizures seem to have the high "adequacy" or "quality" that have been claimed to reflect positive predictive power for the outcome of an ECT course. The induction of well-generalized seizures can be potentially influenced by several variables. One major variable is concurrent medication including anesthetic drugs, since most anesthetic drugs are potent anticonvulsives. We hypothesized a negative influence of anesthetics and benzodiazepines but a positive effect of antidepressants and antipsychotics concurrently applied during ECT on seizure adequacy. METHODS We included inpatients (n = 41) with a DSM-IV-diagnosed major depressive episode treated with ECT (411 ECT sessions) during a period of 20 months (May 2005 to December 2006) in an open label and noncontrolled study. A repeated measurement regression analysis was performed with 8 seizure adequacy parameters as dependent variables. We indirectly quantified narcotic agent influence with bispectral index monitoring. RESULTS In contrast to the impact of psychiatric comedication, this measure of "depth of narcosis" prior stimulation turned out to influence most seizure adequacy parameters in a highly significant manner. CONCLUSIONS Thus, we concluded that the anticonvulsive properties of narcotic agents have much higher influence than concomitant psychotropic medication. Our data support the view that a significant influence of concurrent psychotropic drugs on seizure adequacy markers is missing, especially when directly compared with other confounders like stimulation energy, age, and depth of narcosis. The latter suggests to further prove the idea that lighter anesthesia is indeed an important tool to get patients faster into remission.