Sustained stress can cause myriad health problems. When you are under stress your body is flooded with a hormone called cortisol.
In short, infrequent bursts it isn't harmful. It's your body's natural response to stressful situations. But when you are constantly bombarded with cortisol it leads to systemic inflammation. Systemic inflammation is linked to everything from heart disease to cancer to diabetes.
This is not my opinion. It is my psychiatrist's explanation for why taking benzodiazepines is better than leaving severe generalized anxiety untreated. Aside from making you miserable it takes a very real toll on your health.
Of course, the medication takes a very real toll on your health too, so I suppose you can pick your poison. I finally decided I'd rather not be in a constant state of panic. Benzos may not be much if any healthier but at least I feel better. Mostly.
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"That isn't damage. It's proof of what you can survive."
- Joanne M. Harris, The Testament of Loki