Okay.....I do not know diddly squat about this topic but still am willing to share a few of my thoughts on this subject as far as I have dealt with it..LOL!
Okay...someone in my life recently told me that their spouse has a "sex addiction" problem   (which according to this person  is what lead to the problems they have always had in their marriage and they seem to always fall back on the "excuse" that the problem is that the spouse has a "sex addiction")   ..... now in this particular case all that I know is that the spouse they are referring to seemed to have no problem whatsoever being faithful to his first wife....so it seems to me as though  what the current spouse deems as "sex addiction" must be something that has cropped up in her marriage to him.
now..... 
I really don't know a dad-gum thing about this sort of sex "addiction" thing...but my own 2 cents is that I honestly would have to believe that a lot of times the reason people find themselves "Looking for love in all the wrong places".... is because for some reason....they do not feel really loved at home...and a lot of times it is simply a matter of real communication and real honestly felt connections that do tie a couple together ....
anywhoo...
here is a link I found defining the topic...and of course every case would be different in an apples to apples type of thing :).... 
1.  WHAT IS SEX ADDICTION?
    Sex addiction is a method of medicating feelings  and/or coping with
 stress to the degree that one’s sexual behavior becomes the  major 
coping mechanism in their life. The individual often cannot stop the  
sexual behavior for any great length of time by themselves. The sex 
addict  spends a lot of time in the pursuit of his or her sexual 
behaviors/fantasies or  they have a binge of sexual behaviors. 
  
2.  WHY DO PEOPLE BECOME SEXUALLY  ADDICTED?
    This is different for every sex addict but  generally speaking there
 are biological, psychological, and spiritual reasons.  The following is
 a short explanation. The 
biological  addict is someone who has
 conditioned their body to receive endorphins and  enkephlines (brain 
chemicals) primarily through reinforcing a fantasy state  with the 
ejaculation that sends these chemicals to the brain. 
Psychologically,
 the need to medicate or  escape physical, emotional or sexual abuse can
 demand a substance and the early  addict finds the sex medicine usually
 before alcohol or drugs. 
Spiritually, a person is filling up 
the  God hole in them with their sexual addiction. The addiction is 
their spirituality; it comforts  them, celebrates them and is always 
available and present.  Then there is the sex addict who can a mix of 
two or even three of the above  reasons. This is why a specialist in sex
 addiction is the best route for  recovery from sex addiction.