Bipolarity as a Factor in Relapse After ECT: New Study From Japan

 Out on PubMed, from investigators in Japan, is this study:

Factors causing a relapse of major depressive disorders following successful electroconvulsive therapy: A retrospective cohort study.

Kurimoto N, Inagaki T, Aoki T, Kadotani H, Kurimoto F, Kuriyama K, Yamada N, Ozeki Y.World J Psychiatry. 2021 Oct 19;11(10):841-853. doi: 10.5498/wjp.v11.i10.841. eCollection 2021 Oct 19.PMID: 34733646 

The abstract is copied below:

Background: Electroconvulsive therapy (ECT) is used to treat major depressive disorder (MDD). Relapse is often observed even after successful ECT, followed by adequate pharmaceutical treatment for MDD.

Aim: To investigate the diagnostic factors and treatment strategies associated with depression relapse.

Methods: We analyzed the relationships between relapse, the diagnostic change from MDD to bipolar disorder (BP), and treatment after the initial ECT. We performed a 3-year retrospective study of the prognoses of 85 patients of the Shiga University of Medical Science Hospital. The relative risk of relapse of depressive symptoms was calculated based on the diagnostic change from MDD to BP. A receiver operating characteristic (ROC) curve was generated to evaluate the predictive accuracy of diagnostic changes from MDD to BP based on the duration between the first course of ECT and the relapse of depressive symptoms.

Results: Eighty-five patients initially diagnosed with MDD and successfully treated with ECT were enrolled in the study. Compared with the MDD participants, more BP patients experienced relapses and required continuation and/or maintenance ECT to maintain remission (65.6% vs 15.1%, P < 0.001; relative risk = 4.35, 95%CI: 2.19-8.63, P < 0.001). Twenty-nine patients experienced relapses during the three-year follow-up. In 21 (72.4%, 21/29) patients with relapse, the diagnosis was changed from MDD to BP. The duration from the first course of ECT to relapse was shorter for the BP patients than for the MDD patients (9.63 ± 10.4 mo vs 3.38 ± 3.77 mo, P = 0.022); for most patients, the interval was less than one month. The relative risk of depressive symptoms based on diagnostic changes was 4.35 (95% confidence interval: 2.19-8.63, P < 0.001), and the area under the ROC curve for detecting diagnostic changes based on relapse duration was 0.756 (95%CI: 0.562-0.895, P = 0.007).

Conclusion: It may be beneficial to suspect BP and change the treatment strategy from MDD to BP for patients experiencing an early relapse.

Keywords: Antidepressant; Bipolar disorder; Electroconvulsive therapy; Major depressive disorder; Prognosis; Relapse.

And from the text:

Moreover,  when  other  psychotic  and  epileptic  symptoms  were  dominant  and  met  the DSM-IV-TR[19]  diagnostic  criteria,  the  diagnosis  was  changed  to  schizophrenia  and epilepsy, respectively.

Written  informed  consent  was  not  obtained  because  of  the  retrospective  nature  of  the study

This study is a mixed bag. Although it is retrospective, the methods sound like the authors want the reader to believe it was semi-prospective. The above diagnostic sentence in yellow highlight is a red flag. 

So, I think we should appreciate the "forest" and take the "trees" (the details of the results) with a grain of salt. The idea that early relapse after successful ECT is more common in patients either misdiagnosed, or not yet diagnosed, with bipolar disorder is very interesting and important. The special role of lithium for such patients, as well as for MDD patients, in relapse prevention is also very important and in need of further study and implementation.

The risk I fear here is seeing bipolarity under every rock, that is, having way too low a threshold for conversion of the diagnosis. 

This is a complicated paper and I hope blog followers will read it carefully and comment with your opinions about it; a full read will be ~ 20 minutes.