Dr. Timothy Vollmer, the director of Neurology Clinical Research at the University of Colorado-Denver, even says that such activity can be beneficial.

CNN: STORY HIGHLIGHTS

And researchers from the University of Colorado, Denver, are planning a high-altitude research trip to Bolivia with 24 study participants.

WSJ: Mayo Clinic Researchers on Everest Study High Altitude's Effects on the Body

Holmes was a doctoral student in Aurora, in the neuroscience program at the Anschutz Medical Campus of the University of Colorado, Denver, until he withdrew a month before being arrested outside the bullet-riddled movie theater.

CNN: STORY HIGHLIGHTS

Holmes was a doctoral student in the neuroscience program at the Anschutz Medical Campus of the University of Colorado, Denver, in Aurora, until he withdrew a month before being arrested outside the bullet-riddled movie theater.

CNN: STORY HIGHLIGHTS

In the article, New York-based reporter Jana Winter cited anonymous law-enforcement sources who said shooting suspect James Holmes sent a notebook containing violent drawings to a University of Colorado, Denver psychiatrist before the attack.

NPR: Ruling Again Delayed On Sources In Colo. Shootings