In the brain, this inflammatory process enhanced indoleamine2,3-dioxygenase-1 (IDO-1) activation with subsequent alteration in kynurenine/tryptophan levels, which can be one of the main causes of the development of depression in CVD patients (Raucci et al. 2019; Wang et al. 2019; Zhang et al. 2019a; Tong et al. 2020; Wang et al. 2020; Xu et al. 2020; Wahid et al. 2021). Here, IDO1 is linked to major depressive disorder.