All characters do, indeed, suffer from despair, yet deception may be a more accurate description! Mrs. Alving must face the despair that she could possibly have helped Oswald, her son. Yet, she deceives Oswald from keeping her husband's illness from him. Oswald despairs of his condition, yet he also does not face his own reality. Regina is also at the heart of this deception.
If it is true that "the sins of the father are visited on the children" than this drama explicates the despair caused from one generation to the next. However, isn't Ibsen asking us to look more deeply at how we personally respond to despair and allow it to influence our life?