BDNF and depressive disorder: In line with this, a study by Teng et al. found that decreased BDNF levels wereassociated with depression and cognitive decline, further suggesting the role of BDNF in mental health disorders [40].Similarly, a study by Correa et al. reported a significant reduction in BDNF levels in individuals with periodontaldisease, supporting the notion that BDNF may play a key role in the pathophysiology of both neuropsychiatric and periodontal conditions[14].