Predictors of the short-term responder rate of Electroconvulsive therapy in depressive disorders - a population based study

Background: The aim of the present study is to investigate the responder rate of Electroconvulsive therapy, ECT, in clinical routine work and to define clinical characteristics predictive of response to ECT. The main hypothesis is that the responder rate of ECT might be lower in clinical routine than in controlled trials. Methods: This is a population-based study of all patients (N = 990) treated with ECT for depressive disorders, between 2008-2010 in eight hospitals in Sweden. Patients with Clinical Global Impression-Improvement scores of 1 or 2 (much improved) within one week after ECT were considered responders to ECT. The predictive values of single clinical variables were tested by means of chi-squared tests and the relative importance was tested in a logistic regression analysis. Results: The responder rate was 80.1%. A higher proportion of older patients (>50 years) responded (84.3% vs. 74.2%, p < 0.001). Psychotically depressed patients responded better (88.9% vs. 81.5% for severely depressed and 72.8% for mildly depressed, p < 0.001). There were no significant differences in responder rates between patients suffering from bipolar, first or recurrent major depressive syndromes, or a depressive episode of schizoaffective disorder. Patients with personality disorder had a lower responder rate (66.2% vs. 81.4%, p < 0.001). Also, outpatients had a lower responder rate (66.3%) compared to inpatients (83.4%, p < 0.001). In the logistic regression analysis, inpatient status, psychotic symptoms, absence of schizoaffective disorder and older age were independent factors associated with response to ECT. Conclusions: This study focuses exclusively on the short term responder rate with ECT in clinical practice. Similarly to results from controlled trials a high responder rate is reported. Older patients, more severely ill patients, psychotically ill patients and patients without personality disorders had the highest responder rates. Inpatients may have better outcome with ECT than outpatients.