Severe tinnitus generates a vicious cycle because, as a source of stress, it activates the Hypothalamus-Pituitary–Adrenal axis, leading to increased levels of cortisol, reduced BDNF, and elevated norepinephrine, serotonin, and 5-hydroxyindoleacetic acid (Patil et al., 2023). This evidence concerns the gene BDNF and Tinnitus.