Healthcare providers typically diagnose attention-deficit/hyperactivity disorder (ADHD) in childhood. But some people don’t receive a diagnosis until adolescence or even adulthood. Teenagers with undiagnosed ADHD may struggle even more with the symptoms of ADHD as they enter adolescence. Other adolescents have unrecognized learning disorders, or ways of processing that differ from the norm. Falling grades are a red flag for unmasked ADHD, learning disorders or signs of stress, including depression