GSTM1 and major depressive disorder: In order to ensure that the model is both efficient and concise, and considering the simplicity and operability in the process of practical clinical application, the Lambda.lse value (Lambda = 0.02787465) with the cross-validation error within the range of plus or minus one standard error of the minimum error was selected as the optimal penalty coefficient in our study, at which time the model contained 13 variables, including age, gender, BMI, residence, smoking, arthritis, cognitive function, depression, social participation, ADL, PEF, DBP, and Hb.