Electroconvulsive therapy (ECT) is one of the earliest treatments available for the treatment in psychiatric disorders and has a distinct position in psychiatric treatment guidelines. In last many years there have been a lot of research done by modifying various electrical parameters  of ECT to address its cognitive adverse effects without compromising efficacy. One of them is the alteration of pulse frequency of electric current administered in ECT. There have been only 2 RCTs and few cases series done to examine effect of ECT pulse frequency. The results of them indicated positive effect on efficacy, reduction in seizure threshold with lower pulse frequency, without affecting the cardiovascular response. The examination of cognitive effects, detailed morphology of EEG recordings and other parameters of adequate seizures have not been conducted. Further, these studies were done in patients with depression, when schizophrenia is an equally considered indication of ECT in Asian countries. Hence, this study is planned to examine the effects of reduction in pulse frequency (50 pps from 125pss) of bifrontal ECT in patients with schizophrenia on various cognitive and clinical outcomes, seizure threshold and physiological parameters including EEG morphology, which all indicate the adequacy of seizures. This was carried out as the double blind randomized controlled trial through 2 MD Psychiatry thesis dissertations in National Institute of Mental Health and Neurosciences, Bangalore from September 2018 to October 2019 after taking approval from Institute Ethical Committee.

We could recruit 46 patients with schizophrenia including both groups. The patients in 50pps and 125pps groups were comparable in both socio-demographic and baseline clinical variables. In terms of clinical efficacy for schizophrenia, both the groups showed similar improvement in psychopathology, catatonic behaviour, and general ward behaviour as well as global assessment. There was neither difference in 2^nd nor 6^th ECT session EEG and CVS parameters between the 2 groups. In each group, all these parameters also didn’t differ between 2^nd and 6^th ECT sessions recordings. Seizure threshold for ECT also were similar in 50pps and 125pps groups.

On comparison of performance on cognitive variables assessed before 1^st ECT session and Post 6^th ECT session (as calculated by Wilcoxon signed-rank test), there was statistically significant decline in autobiographical memory (p=0.048), word short delayed recall ( p=0.035), word recognition (p=0.011), visual recognition (p=0.027) and phonemic fluency (p=0.007) in 125pps group. In contrast, 50pps group performed similarly on these cognitive variables in both assessments. However, significant improvement was noted in visual delayed recall (p=0.011) in post 6^th ECT session assessment compared to 1^st ECT session in 50pps group. This difference was absent in 125pps group. None of these pre-post differences between 50pps and 125pps groups was evident in time*group RMANOVA. The clinical status of patients posted for ECT precluded some of the patients from co- operating for pre ECT cognitive assessments, which reduced sample size further during RMANOVA. There is a need to conduct similar study with larger sample size in order to confirm findings of this study and also to see the effects in sub-groups such as elderly.