Recent studies with rats, conducted by CU Boulder Neuroscience professor Dr. Ryan Bachtell, indicate that teens who indulge in excessive amounts of caffeinated beverages such as coffee, sodas, and energy drinks tend to develop behaviors that are consistent with anxiety disorders. These behaviors persist even after the caffeine use. Although it has been common for teens to drink caffeinated beverages for decades, these days teens are drinking larger quantities, and are also energy drinks that contain larger amounts of caffeine. Because the teenage brain is still developing, the effects of caffeine are not innocuous. You can access more information about the study HERE.
In my opinion, it makes sense for teens to limit caffeine by ordering smaller sizes, drinking 1/2 caf or decaf, and avoiding the use of energy drinks, especially if they are experiencing anxiety or when there is a family history of anxiety issues.