In the lives of those experiencing anxiety, anxiety has almost always served a purpose as a survival function at some point. Some anxiety can even produce desirable results, as it can motivate individuals to complete needed tasks, to perform at their best, or to recognize safety risks. Most successful, motivated individuals have likely had some degree of anxiety that helped them push themselves to where they are now. Anxiety becomes a problem when it is pervasive, distressing, or leads to inhibiting behaviors, likely due to an altered perception of the world. This can look like consistently worrying about the same issues despite no evidence to support the worries (worrying that one has cancer despite being healthy, worrying that one will fail graduate school when one has high grades, worrying that one's partner will suddenly die), being on high-alert and having distressing, intrusive recollections following a traumatic experience, or sometimes experiencing stress in the body through trembling, not being able to get a full breath, sweating, heart palpitations, or unexplained muscle tension.
Generalized anxiety disorder (GAD), phobias (including social anxiety), posttraumatic stress disorder (PTSD), obsessive compulsive disorder (OCD), and panic attack disorder are all anxiety disorders that people seek treatment for. EMDR (Eye Movement Desensitization and Reprocessing) is considered to be one of the most effective therapeutic treatments available for trauma.
Read more about anxiety here.