I thought mine would be a simple interview to weed out possible psychoses like OCD, or people who would go psycho after they were suddenly skinny. Nope. Mine. Was 4 hours long. The first hour was the interview which started normal enough. One moment he was asking about my line of work and if I enjoyed it, etc, then suddenly asks if I hear voices lol. I actually 'lol'd but be kept a straight face, and I thought that was one strike lol. He then proceeded to lead me through mental exercises I remember doing on clinically insane patients while in nursing school! The last 3 hours consisted of me taking several tests on paper. One test was a few hundred questions long.
In a nutshell, it wasn't cake like I read online most people experienced. I asked him at the follow up what type of personalities he would NOT allow to have surgery, and he said emotional eaters, addictive personalities, and people with poor coping mechanisms. Also people currently undergoing clinical depression. As he stated, your WLS journey would be most successful if those factors are treated before surgery happens.
Hope this helps, and best of luck!