Extroverts often incorrectly assume that introverts are suffering. Introverts internalize problems; we like to take things inside and work on them there. Extroverts prefer to externalize and deal with problems interactively. Because of this difference, introverts may seem psychologically burdened, while extroverts spread the burden around and seem healthier — from an extroverted standpoint.
But note that I said introverts like to take problems inside. Sure, an introvert can overdo it, but so can the extrovert who feels compelled to express every unresolved thought or emotion. The former gets depressed or anxious and goes to therapy; the latter sends others to therapy.