Based on this research, I am not sure that any illness should be considered "psychosomatic" or "all in one's mind." Illness exists in the mind, body and brain. And all illness should be taken seriously.
Instead of an assessment (which implies judgment) and advice (which implies expertise), what someone who's mentally distressed, in any context, needs first, mentally and emotionally, is some acknowledgment and support.
Breaking through upper limit problems require you to show up and keep showing up fully, no matter how scary or challenging it may be. When you become aware of hitting your upper limit, pivot. Be willing to look at the real issue.
If day-to-day stress and anger and anxiety are not causes of hypertension, do I believe that there is a mind/body connection in hypertension? Yes, I absolutely do. But the connection is very different from what most people think.
The golden rule: an underlying medical illness or medication side effect has to be ruled out before ever deciding that someone's symptoms are caused by mental disorder. And the underlying medical illness may take time to declare itself.