HSP (Highly Sensitive Person) is a kind of personal “trait” that those who seem to be naive, sensitive, and introversive have.
This is by nature, but not any disease.
This is just a psychological concept to classify people into two groups, tough and sensitive.
In a society and generation that prefer to those who are active and socialized, the people of HSP are often underestimated unfairly, for example, (1) they are not socialized, (2) they are too worried and not active.
However, the HSP people are also uniquely talented.