As someone who has experienced this from the inside let me share with you exactly what is going on...
A large part of anxiety is the result of basically running mental simulations of the world with "negative" assumptions. Thus, people who are better at cognitive simulation (i.e. high IQ) are naturally going to have a greater capacity for worry. That being said, if you train your mind to stop running simulations all the time (mindfulness) or just start running simulations with positive assumptions, that anxiety can be eliminated without any impact on intelligence whatsoever.
A large part of anxiety is the result of basically running mental simulations of the world with "negative" assumptions. Thus, people who are better at cognitive simulation (i.e. high IQ) are naturally going to have a greater capacity for worry. That being said, if you train your mind to stop running simulations all the time (mindfulness) or just start running simulations with positive assumptions, that anxiety can be eliminated without any impact on intelligence whatsoever.