Memory is the concern most often raised by people considering ECT for depression, and it is a reasonable one to weigh carefully. A 2024 review brought together ten studies covering 868 people with major depressive disorder, specifically to examine what happens to memory and thinking over the longer term.
The findings are not a simple yes or no. The review suggests that much of the disagreement in this area comes down to measurement. Older studies mostly relied on general cognitive tests, which were not designed to detect the particular kind of memory change ECT can cause. Unsurprisingly, many of them found nothing.
When the researchers looked instead at studies using a newer, purpose-built measure, a different picture emerged: evidence of a lasting effect, particularly on longer-term memory. This deserves to be stated plainly. The review does not dismiss the concern about lasting memory changes after ECT. It supports it, while also showing that many earlier studies may have looked reassuring simply because they were not measuring the right thing.
This does not mean ECT is the wrong treatment. For severe depression, it remains one of the most effective options available, and for some people it is lifesaving. It does mean the memory trade-off is real and worth discussing openly with your treating psychiatrist. If you are weighing up ECT, or struggling with depression more broadly, it is worth speaking with a professional about what fits your situation.
What the study did
Guo et al. carried out a systematic review and meta-analysis, a method that statistically pools results from multiple separate studies to produce a more precise, combined estimate than any single study could give. They gathered 10 studies (five randomised controlled trials, where participants are assigned by chance to different conditions to reduce bias, and five quasi-experimental studies, which compare groups without full randomisation) covering 868 people with major depressive disorder (MDD). Their specific question was why research on ECT and long-term cognition has been so inconsistent.
Why the disagreement exists
Most earlier studies used general cognitive screening tools such as the MMSE (Mini-Mental State Examination) or MoCA (Montreal Cognitive Assessment). These were originally built to flag broad impairment, such as in dementia, not the narrower, specific changes ECT might cause. Guo et al. compared these against a newer, purpose-built instrument called the ECCA (Electroconvulsive Therapy Cognitive Assessment), designed specifically to detect ECT-related cognitive change. The central finding of the review is that the tool used changes the answer you get.
What it found
When studies used the ECCA, the pooled analysis found a significant long-term decline in overall cognitive function (SMD = -0.94, 95% CI [-1.33, -0.54]). SMD stands for standardised mean difference, a way of expressing how large a difference is in comparable units across studies that used different tests; a value near 0.94 represents a fairly large effect. Breaking this down by cognitive subdomain, only long-term learning ability showed a statistically significant decline (SMD = -0.37, 95% CI [-0.55, -0.18]). Memory, attention, language, and spatial perception/orientation all showed changes that were not statistically significant, meaning the confidence intervals crossed zero and a true effect can't be confirmed from this data. Notably, executive function and processing speed actually improved after ECT (SMD = 0.52, 95% CI [0.29, 0.74]), a moderate positive effect.
Why it matters
This is a more precise picture than "ECT harms memory," which is the assumption many people carry into treatment decisions. The measurable long-term impairment detected here was concentrated in learning ability specifically, not memory, attention, or language, and was only reliably picked up using the newer, more sensitive ECCA tool rather than the general screens most older studies relied on. At the same time, executive function and processing speed improved, which may partly reflect that depression itself impairs cognition, and effective treatment can lift some of that fog. The authors suggest these findings are relevant to how international clinical guidelines describe ECT's role in treating MDD.
Limits
Ten studies is still a modest evidence base, and mixing randomised trials with quasi-experimental designs means some included studies carried more risk of bias than others. The review cannot tell us why learning is specifically affected, only that it is. It also can't say how these changes feel or function in daily life for a given person, since it works with statistical averages across groups, not individual experiences.
If you're weighing up ECT, or noticing changes in your thinking after treatment, please talk it through with your treating psychiatrist or a qualified mental health professional — you don't have to make sense of it alone.