BDNF and major depressive disorder: The pilot study suggests that staircases may have a relationship with physical activity, while spatial novelty may potentially be driven by the presence of more floors aside from the staircase’s use or lack of use We suggest that physical activity, arguably through the presence of stairs, explains the reduction in depression by 13.4%, where this reduction acts as an antidepressant that is evidenced in earlier research to be in a linear relationship with neurogenesis through the neurotrophic factors such as BDNF [88,89].