Complex sentence: A nervous breakdown is not limited to any one type of person: anyone can have this breakdown, but if someone is under a lot of stress and has a family background of mental disorders, they can be more likely to have one.
Split into simpler sentences: A nervous breakdown is not limited to any one type of person. Anyone can have this breakdown, but if someone is under a lot of stress and has a family background of mental disorders, they can be more likely to have one.