Very good and I believe true post.
I wouldn't go so far as to say that all illnesses or dis-ease are psychosomatic, but so many indeed develop due to outside influence.
So often the way we treat others, or even perceive others can progress and develop symptoms which translate into discomfort, even severe pain when they enter our thoughts.
A friend of mine left her mother to travel overseas to be with her love. Her mother became ill. Although my friend did visit her mother occasionally, she began to suffer from severe pain...so debilitating that she had to give up her employment and could no longer travel to visit her. When her mother died, my friend "miraculously" recovered from her crippling pain completely. She now thinks her pain was psychosomatic. Perhaps her mother's cancer was also brought on from losing her only daughter?
When my father was made redundant after working in his job for many years, he became very depressed and developed cancer. We are all certain that it was the stress that caused the cancer cells to flourish in his body.