If you read the articles, you will see that both articles explore factors that contribute to the development as well as the maintenance of anxiety disorders, so the articles are addressing prevention as well as treatment. Both papers cite studies that used healthy individuals as well as individuals who have been diagnosed with an anxiety disorder by a physician and explore evidence for mindfulness as a “psychotherapeutic change agent.”  
 The practice of mindfulness involves paying attention to the present moment and noting for oneself that anxiety related thoughts (as well as all other thoughts) as transient events (arising and ceasing, when the conditions are there). Observing this way can be done regardless of whether an individual has been formally diagnosed with an anxiety disorder by a physician or not. 
 By the way, I noticed that the article by Patel and Fancher (2013) did not include mindfulness interventions, and I was wondering if this needs to be stated as well, especially because it makes the global statement “As of 2013 there are no effective measures to prevent GAD in adults.”  

 Happy New Year!