The cause of wife infidelity is relationship addiction. It is not caused by problems of marriage, sex, love, emotions, or desires. The wife has developed a psychological disorder in two components of psychology. She has the disorder of memory of emotion in which she cannot stand even the smallest wound, and expression disorder in which she is addicted to the object of addiction, the adulterer in this case, and she has self-conviction that her ideas are right. 

She develops relationship addiction when she stores in her memory the adulterer's expressions such speech, actions, and facial expressions as attention and consolation, or when she develops desires for the distorted relationship that provides her with attention and consolation. Then, she activates her wounds toward all the attention and consolation from other people than the adulterer including her family, friends, and coworkers, and tries her best to avoid or remove sources of wounds. She begins to employ sexual expressions to develop, maintain, and reinforce relationship addiction, and grow self-conviction that she is in love with the adulterer and living a happy life.      

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Relationship addiction is not activated toward her husband, children, family members, and people who she remembers that have inflicted wounds upon her.     

She lives her life only with reference to her own distorted thought maximizing sexual expressions whenever possible and displaying hysteria when she cannot hold her wounds inside, which happens often. She may end up destroying normal and healthy relationships with family, friends, and coworkers. Her relationship addiction keeps getting aggravated unless treated properly.

She may be able to adopt proper treatment when she realizes that her ideas and her life have gone wrong at some fundamental level. She may be in excruciating pain due to conflicts with the adulterer or realize that her hysteria is destroying herself and other people. The husband needs to treat his post traumatic stress and build happiness ability. Then, he can help his wife treat relationship addiction. Living with relationship addiction or post traumatic stress is far from living happily. You yourself must gather up the will power and make efforts for happiness of yours and your loved ones.