Hey Coalfire,
I'm not a geneticist so forgive me if I use the wrong terminology, but the gene associated with nal response is located at Rs1799971 and is called OPRM1. The possible genotypes are AA, AG, and GG. AA is normal. AGs have a better chance of responding to nal than AAs. And GGs have an even better chance of responding to nal, but have an increased likelihood of developing alcoholism, and an increased aversion to social rejection. There is a much more in depth description of this at
http://www.snpedia.com/index.php/Rs1799971Here is a chart from the above website of the percentage of each genotype in different sample populations.

Orange is AA, Green, AG and Blue GG. Most on this board will be interested in CEU, which is a sampling of a western and northern European population. I probably relate most to HCB, which is a Chinese population (I'm Vietnamese) Most people are AA and that group has about a 55% positive nal response. If you have at least one G then your chances go up to 87%. You can see the GGs are on average, less than 10% of the population. I am GG.
As for my experience with alcohol, I believe I was an alcoholic from the first time I got drunk (18, Freshman year of college). I definitely experienced the euphoria. Luckily, my first 3 years, I didn't have much access to alcohol, so I only got drunk maybe once every several months at parties but I was constantly thinking about the next time. Alcohol made me feel comfortable at social functions where otherwise I would have been shy (though it still did not help with the ladies because I would get trashed so quickly). As soon as I turned 21, I started drinking alcoholically almost every night. There was no build up from regular drinking to alcoholic drinking. It was straight into alcoholic drinking for me. Alcohol made me feel alive and alert, not sedated and I did panic if I ran out, so I always made sure I had enough. I would not stop until I passed out. I knew I had a problem almost from the beginning.
As for my fear of rejection... I never had a girlfriend in high school or college mainly because I was too scared to ask girls out and because I was too picky (plenty of girls liked me but they just weren't the ones I was interested in). I had and still have an intense fear of rejection, though it is not as bad now that I'm older. I did not have my first real girlfriend until I was 29 years old. And even with her, it took me a year and a half before I worked up the nerve to kiss her. This is all very personal stuff and I can't believe I'm sharing it, but it illustrates the depths of my fear of rejection. I have plenty of friends, have a good education, decent job, come from a respectable, well-off family, am pretty good-looking (yes, I'm tooting my own horn), but my fear of rejection, I believe has held me back from finding that special someone. When my girlfriend dumped me because of my drinking, I took it very hard and I still am even 6 months later. I'm in pain everyday and I still break down in tears at random times.
Fear of rejection and alcoholism has defined my life in so many ways and it is strange to think that it could be caused by a single gene in my DNA. Luckily, this gene also predicts I will be successful with nal. I hope I've answered most of your questions Coalfire, don't hesitate to ask if you have others.