Find out the factor that does the most brain damage.In the largest study of its kind, researchers have identified the top factors that age the human brain. Psychiatrist and author Dr. Daniel Amen reveals a shocking observation from his study—marijuana was the second biggest culprit in brain aging. It created more damage than smoking, alcohol, bipolar disorder and ADHD. Tune in to find out the factor that does the most damage. Plus, learn expert-approved ways, like best foods to eat and activities to try, to boost brain activity and keep your noggin young. Bonus! Is Holding It In Harmful to Your Health?