Yes your relationships can cause mental disorders, and yes if you have a undiagnosed mental disorder already your relationships can aggrivate and bring out more problems associated with having the mental disorder. the mental disorder will be there until you get treatment. the symptoms may lessen when you are out of the abusive relationships but the symptoms / problems can keep popping up in your life unexpectedly until you recieve treatment.

Example a person who has undiagnosed seasonal depression can enter into an abusive relationship. that abuse can cause the person to become withdrawn, depressed, anxious, have nightmares, phobic (post traumatic stress disorder, anxiety disorder, panic disorder) and can make their seasonal depression more severe. finally out of the abusive relationship the person can continue to go through their previos PTSD symptoms plus flashback (reliving the abusive relationships as if its still happening), anxiety, phobias, severe seasonal depression. as time goes by the symptoms lessen but suddenly you are having the same symtomsagain because you saw someone who remined you of the abuser, or something that remided you of the abuse. that will keep popping up for you until you get treatment for it.