[clevercode]

The first study you link to does not appear to address the correlation/causation issue whatsoever. Specifically: "The study acknowledges that people who regularly run marathons, like many of the study's participants, may be genetically predisposed to running long distances."

The second link describing neurogenesis stimulation is more interesting due to the fact that they are tracking actual changes in the participants over the course of the study.

For the record, I do not doubt for a moment that exercise has numerous positive benefits, both physically and mentally.