Not too many days ago, when I was furious at some supplier over the phone, I was told by a friend overhearing me that anger was a possible source of my early heart attack. Age 74 is not really so early.
Nevertheless it is a prevailing theory among many people who follow the psychotherapeutic world that anger is a source of stress on the heart. Personally I find it frequently useful in dealing with intransigent problems that it provides great satisfaction. I also do not remain angry 2 minutes after I express myself.
The intellectual problem with this issue is that psychotherapy holds the exact opposite theory with equal certainty.
When anger is bottled up it is harmful to the heart and the psyche. Anger that is bottled up is presumed to leak out in unexpected and disturbing ways.
I have explained to many American friends that I have only once seen an expression of anger in Japan. I am almost always informed by Americans that this is a form of social repression and must explode in some other behavioral channel.
I think both of these models of anger expression and anger repression are fanciful. Having a model with two equally valid opposites is evidence of the pseudo-intellectual nature of psychotherapy.