Is the cortisol and verbal fluency association stable within individuals?
The reported interaction between cortisol awakening response and Val66Met BDNF polymorphism in verbal fluency raises a longitudinal question: does variation in the cortisol response precede reproducible within-person changes in fluency, or mainly distinguish people at one assessment? Repeated cortisol and cognitive measurements would help estimate day-level variability, practice effects, and temporal ordering. The result that matters is whether sustained change predicts later cognitive decline or preserved function beyond baseline performance.
