OBJECTIVE: To probe into the efficacy of Escitalopram oxalate tablets combined with modified electroconvulsive therapy (MECT) in patients with bipolar disorder and depressive episode and its effects on serum brain-derived neurotrophic factor (BDNF). METHODS: This study was a prospective randomized controlled trial, which started in Mar. 2019 and ended in Oct. 2020. A total of 114 patients with bipolar disorder and depressive episode admitted into Jining Psychiatric Hospital were extracted, and the sample size was determined by the sample size of the superiority test. Excel function was used to generate 114 random numbers, and patients were assigned according to the order of admission. Odd and even numbers were set as control group and study group respectively. During the clinical investigation, there were 7 cases of missed and lost follow-up, and 107 cases completed the experiment, including 53 cases in the control group and 54 cases in the study group. The control group was treated with MECT, while the study group received Escitalopram oxalate tablets combined with MECT. The depression status of two groups before treatment and after treatment of 8 weeks was evaluated by Hamilton Depression Scale-17 (HAMD-17), and the serum BDNF level was detected, cognitive function was assessed by Trail Making Test (TMT), the efficacy was evaluated and the incidence of adverse drug reactions was analyzed. RESULTS: The total effective rate of the study group was 92. 59% (50/54), significantly higher than 71. 70% (38/53) of the control group, with statistically significant difference (P<0. 05). After treatment, the HAMD-17 score of two groups was significantly lower than that before treatment, and the HAMD-17 score of the study group as lower than that of the control group, with statistically significant difference (P<0. 05). After treatment, the serum BDNF level of two groups was significantly higher than that before treatment, and the serum BDNF level of the study group was significantly higher than that of the control group, with statistically significant difference (P<0. 05). After treatment, TMT-A and TMT-B of two groups were significantly shorter than those before treatment, and those of the study group were significantly shorter than those of the control group, with statistically significant difference (P < 0. 05). There was no significant difference in the incidence of headache, nausea, vomiting, dizziness, short-term memory disorder between two groups (P > 0. 05). CONCLUSIONS: The efficacy of Escitalopram oxalate tablets combined with MECT in patients with bipolar disorder and depressive episode is significant, which can significantly alleviate the depression, effectively increase the level of BDNF and improve the cognitive function with higher safety. [ABSTRACT FROM AUTHOR]