[NeuroBeautiful]

Addiction can worsen a pre-existing psychiatric condition. It can be debilitating physically and cognitively t if you are dependent on substances for instance(as an example but any addiction can impact you in several ways). However like Jenna said, I don't think addiction is a disability in itself but rather a problematic way to cope. Think of a child at school who gas a learning disorder. If overlooked, it can seem that the secondary problems such as procrastination on homework is the main issue when really there can be a hidden learning disability and the procrastination emerged from the emotional difficulties of struggling with school work and not knowing why.
I think addiction works that way too (it is my personal observation that there are parallels between procrastination and addictive tendencies as both are about running away from an underlying emotional problem. In fact procrastination is like an avoidance habit and can simoltaneously lead to addiction of activities like gambling and gaming)

In other words the addiction and disability are related but not one in the same. You can have one without the other. Disability seems like it is the more of a root cause than the addiction or rather the emotional pain and sometimes trauma that come with a disability. It is possible to cope with a disability in a positive healthy way. However addictions and any other harmful coping mechanism can probably have long term impact on your brain and rest of the body so much so that the addiction leads to a disability or a disabling condition, including physical, medical, mental, emotional or cognitive etc