Anxiety is a common experience, not just in our 20s. The vast majority of mental health disorders like anxiety disorder do emerge during early adolescence or early late adolescence or early 20s. If you're under the age of 25, you've still got some growing to do. Your brain is quite malleable at this time. Being exposed to different influences in your social and physical environment can really have a profound impact on the way that your brain is going to develop.