Assessing the Association Between Electrical Stimulation Dose, Subsequent Cognitive Function and Depression Severity in Patients Receiving Bilateral Electroconvulsive Therapy for Major Depressive Disorder

OBJECTIVE: To assess the relationship between electrical stimulation administered to patients undergoing bilateral electroconvulsive therapy (ECT) and subsequent measures of cognitive function and depression severity.

METHODS: Stimulus dose titrated patients receiving bilateral ECT were assessed with the Cambridge Neuropsychological Test Automated Battery (CANTAB) Spatial Recognition Memory test and Montgomery Asberg Depression Rating Scale (MADRS) at baseline, after 4 ECT treatments and on course completion. Changes in CANTAB and MADRS scores were assessed in relation to electrical dosage, initial stimulus dose, and demographic variables using linear mixed models.

RESULTS: Data pertained to 143 patients (mean age, 56.85 [SD, 14.94], 43% male). Median change in CANTAB score was -10% (-20% to 5%) after 4 ECT treatments and -10% (-20% to 5%) at course completion. Median change in MADRS score was -22 (-33 to -13) after 4 ECT treatments and -14 (-25 to -7) at course completion. Electrical dosage had no effect on CANTAB or MADRS change scores either after 4 treatments or course completion. Improvement in CANTAB score at end of course was associated with female sex (P < 0.05), higher intelligence quotient (P = 0.01), and age. After 4 treatments, improvement in CANTAB score was associated with younger age (P < 0.001) and higher intelligence quotient (P < 0.01). Improved MADRS score at course completion was associated with older age (P < 0.001 at end of course and after 4 treatments).

CONCLUSIONS: Electroconvulsive therapy has significant antidepressant and cognitive effects which are not associated with the total electrical dose administered. Other, unalterable variables, such as age and sex, have an influence on these effects.