I must insist on one point: No psychological factor by itself has ever been identified as being capable of creating that bad seed. In other words, nothing permits us to state that psychic trauma can be the sole cause of cancer. However, as with nutrition, exercise, or the quality of our air and water, certain psychological states can profoundly influence the soil in which the seed develops.David Servan-SchreiberThe Author of this QuoteAuthorDavid Servan-SchreiberFrench physician, neuroscientist and author.