This clinical study is a randomized, double-blind, placebo-controlled trial with an intervention period of 4 weeks. Participants will be patients with moderate to severe depression who meet the inclusion criteria during the screening period. After recruitment written informed consent form will be signed and the baseline evaluation will be done then the treatment period follows. The subjects will be randomly assigned to a control group (escitalopram plus normal saline(NA)) and an ATP group (escitalopram plus adenosine disodium triphosphate(ATP)) in a 1:1 ratio for treatment, with a total number of 120 recruited patients. Assessment will be carried out as an analysis of changes in Hamilton Depression Scale（HAMD-24）, cognitive function test, brain functional network, inflammatory markers, and other indicators in the first, second, and fourth week of intervention which will evaluate the effectiveness of ATP in improving moderate to severe depression preliminarily.