There are few long-term studies of electroconvulsive therapy (ECT). But in Sweden a group of 55 people who received ECT at Lund University Hospital between 1976 and 1983 (all voluntary patients of one psychiatrist) were given various tests over the next few years. At some stage they were divided into those who had developed dementia and those who hadn’t, and this has generated an article (A long-term longitudinal follow-up of depressed patients treated with ECT with special focus on development of dementia, by A. Berggren et al.) in the Journal of Affective Disorders. What the authors of this article were doing was comparing results on various previous tests of those people who went on to develop dementia (on average nearly 10 years after ECT) and those who didn’t. I didn’t find it easy to understand what exactly the time-scale was (who was being tested when), so that may not be a good summary.
I haven’t either been able to work out either when exactly it was decided to divide the survivors into those who had developed dementia and those who hadn’t, but by this time there were 49 people left in the study and 17 (35 per cent) of them had dementia. The authors give some rates of dementia in the population, and according to these, it only reaches about 35 per cent in people aged 90-94, which is a lot older than the ECT survivors. In people aged 70-79 (which I think is nearer to the age of the ECT survivors, from the mean ages given in the table) it is about 3 to 6 per cent. Are the authors worried? Not really, as they say that “Recurrent bouts of depression and the severity of depressive episodes seem to increase the risk of developing dementia”. They found that the people who went on to develop dementia were more likely to have experienced disorientation, confusion and amnesia after ECT, but conclude that this “may indicate an increased vulnerability due to the emergent progress of neuropathology”, without considering any other possible conclusions.