I used to hear this referred to as "cross-addicted", but from what I've read... addiction is addiction is addiction -whether it is drugs, alcohol, food, gambling, exercise, adrenalin or spending - these things activate the "reward" center in the brain. Most release endorphins or other brain chemical that bathes the brain in the feel good stuff. Addicts learn to love this stuff... and then their brains respond by absorbing the chemical faster... setting them up to want more, and more often.
When I first got into 12-step, it was for what could be described as a "relationship" addiction, and my sponsor advised me to keep an eye out, because I would likely identify other areas that I struggle. I already knew I was an alcoholic, but I hadn't drank in 20 years... then I found out I don't take my post-surgery drugs the way normal people do... and I tend to over do the gambling... and I am a compulsive overeater.
All those things release the chemicals that give me comfort, make me feel fulfilled... fill the hole in the middle of me.
Addict behavior is complex and addiction is HUGE - far bigger than "only" getting them/us to stop putting the drugs or drink into their system. There are other obsessive behaviors, selfish behaviors and self-serving behaviors that many of us share... which is why a 12-step or other support program is so beneficial.
I hope that not only will your husband find sobriety and recovery... but that you can also check out some meetings that might help you better understand what you are dealing with. Naranon, Alanon and CODA are all good meetings.
I wish you the best.