My own belief is that addiction is an illness since it's almost always caused by alterations to the brain resulting in cognitive deficit disorders and other symptoms.

As with many illnesses associated with a genetic component some people are more susceptible than others which goes some way to help explain why addictions develop faster than inhibitions in those most at risk

Behavioral/lifestyle choices contribute to many illnesses. Fortunately in most of these cases changes can be made since no cognitive deficit disorders have been induced.

Sadly, with alcohol addiction there's a constant high possibility of relapse due to it's chronic nature and need for lifelong mindfulness.

I go for illness