Experimental: the esketamine group

In the esketamine group, in addition to receiving the combination of pregabalin and duloxetine, patients will also undergo a single intravenous infusion of esketamine. A total of 0.5 mg/kg of esketamine will be diluted in 50 mL of normal saline. The infusion will commence with an intravenous injection of 10 mg of esketamine over 1 minute, followed by a maintenance dose of 8 mg/h. The infusion rate will be adjusted based on the patients' tolerance levels.

Placebo_comparator: the control group

In the control group, patients will receive pregabaline combined with duloxetine. Pregabaline will be administered at a dose of 50-75 mg, twice daily during the first 3 days of treatment, and increase to 300mg daily after 3-7days, then by an additional 150mg daily every 3-7 days as tolerated, up to a maximum daily dose of 600mg. Meanwhile, duloxetine will be prescribed at an initial daily dose of 30mg, and then gradually increased to 60 mg daily after one week if patients tolerate it well.