Patients with bipolar depression treated with ECT in the past (on average 45 months ago with a standard deviation of 21 months) only performed significantly worse on the Californian Verbal Learning Test compared to patients with bipolar disorder not previously treated with ECT.
These bipolar patients previously treated with ECT also had significantly more subjective memory complaints.
These two conclusions were drawn from a recent study in which 3 groups of subjects were compared. A group with bipolar disorder previously treated with ECT at least 6 months before memory assessment, a group of patients with bipolar disorder with an equal past illness burden but that had never received ECT and a group of healthy controls. All groups were matched for sex and age.
Now why was this research done?
Cognitive effects of ECT is largely studied in unipolar depressed patients, seldom solely in bipolar patients.
Unipolar and bipolar disorder differ from each other not only in demographic and clinical features but also in treatment and medications.
Some studies suggest that people with bipolar disorder are generally more likely to have cognitive deficits when euthymic than people with unipolar depression. This might be due to the disease it self or due to medication or both.
Extrapolating results from research with unipolar depression and cognitive side effects of ECT to bipolar patients might for these reasons not be very reliable.
Up until this reasoning I can follow the importance of further research into this matter of side effects of ECT and bipolar disorder. But the method used in this trial doesn’t remotely answer this question alas.
The researchers didn’t focus on the most important side effects of ECT such as retrograde amnesia and anterograde amnesia. They used memory tests not very specific for the cognitive side-effects of ECT.
Confounding factors such as medication used prior to testing and during testing as well as other important clinical variables influencing outcome could not be excluded due to small sample size. The differences found could be explained by these variables instead of ECT treatment.
Patients were not randomized to ECT or no ECT.
So what is the bottom line then?
It is still possible that patients with bipolar disorder will have a different long term outcome after ECT than unipolar patients. This research shows that although not very focused on the usual side effects of ECT the cognitive changes are small and are unlikely to influence the risk-benefit ratio of ECT.
In a recent post I mentioned the opinion that some subjective memory complaints can be considered as a somatoform disorder
A post about a memory test for retrograde amnesia
Everyday memory not affected by ECT
Bipolar disorder and ECT
MacQueen, G. (2007). The long-term impact of treatment with electroconvulsive therapy on discrete memory systems in patients with bipolar disorder. Journal of Psychiatry and Neuroscience, 32(4), 241-249.