The cause of husband infidelity is relationship addiction. It is not caused by problems of marriage, sex, love, emotions, or desires. The husband has developed a psychological disorder in two components of psychology. He has perception disorder with which he cannot stand even the smallest stress, and expression disorder with which he is addicted to the object of addiction, the adulteress in this case and he has self-conviction that his ideas are right. 

He develops relationship addiction when he perceives the adulteress's expression such as speech, actions, and facial expressions as responses, or when he develops desires for the distorted relationship upon the perception of the adulteress's responses. Then, he perceives normal responses of people around him including family members as intense stress, and tries his best to avoid or remove such stress. He begins to employ all his abilities and resources to develop, maintain, and reinforce relationship addiction. 

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He behaves normally with people in general on the surface, but he would live his life only with reference to his own distorted thought. He may end up destroying normal and healthy relationships with family, friends, and coworkers. He will also develop sexual dysfunctions and intermittent explosive disorder, and cannot break away from the pathological condition of relationship addiction without proper treatment.

He may be able to adopt proper treatment when he realizes that his ideas and his life have gone wrong at some fundamental level, and he is destroying normal relationships and other people's lives. At this stage, the wife can help the husband by firstly treating her post traumatic stress and building the environment where he can realize his problems and start the treatment of relationship addiction.      

Both the husband in infidelity and the wife in psychological pain must deeply reflect upon the path to true happiness. Both relationship addiction and post traumatic stress bring about misfortune not only for yourself but also for your loved ones. It is only you yourself who can gather the will power and make efforts to restore your healthy psychology and healthy relationships with other people.