BDNF and major depressive disorder: Binary logistic regression analyses revealed that among patients, a high TyG index level was significantly associated with higher BDNF levels and lower negative factor scores of the PANSS, while a high CTI level was significantly associated with higher depression-hopelessness factor scores of the CDSS and lower negative factor scores of the PANSS (all <i>P</i> < 0.05).<h4>Conclusion</h4>Patients with CS had higher levels of TyG index and CTI, which were significantly associated with the severity of negative and depressive symptoms, as well as BDNF levels.