This mom says it better than I could. She uses some all caps like I would. The thing is: mouth breathing is an epidemic no one is talking about.
I have worked with so many adults who have anxiety, depression, and more. Now I'm seeing so many kids get medicated.
One of the first things I wonder is: Are they breathing well?
We used to chew our food. Like CHEW IT. Because it was raw and we picked it off a bush while we hunted and gathered. But now we make smoothies and eat cheese. With weak tongues comes mouth breathing. If there is any reason for a stuffy nose (animal issues, food allergies, etc.) there is mouth breathing. If not trained when babies there can be mouth breathing.
Google "mouth taping". Sleeping with your mouth closed is critical to health and emotional, mental, and dare I say it, spiritual well being because when you breath IN you breath in YOU.
This mom gives a great story (with a happy ending!) and oodles of research.
Happy breathing! :)