That's completely incorrect though, on all counts.
Having worked with lots of patients with mental health and addiction problems, chronic psychopathologies and addictions can be overcome.
Not in all people and not all the time, everyone is different... but in my experience, the idea that you have (that you are permanently affected) is kind of the point of the OP, it's completely detrimental and acts as a crutch to avoid actually owning up and taking control.
It's all there in the literature, look up treatment resistant schizophrenia and clozapine for example.
Many people have come out of prolonged (chronic) severe depression with a combination of lifestyle changes, medication and therapy.
Some people may not have the means, willpower or support to make these changes initially, but that doesn't mean they are incapable of completely getting over the psychopathology with the right help.
This whole AA style 'we are all always addicts' has never sat right with me at all. I have been both physically and psychologically dependent on alcohol (aka addiction) at periods in my life.
These are measurable, delerium tremens is measurable, the amount of benzodiazapine needed to assist with that GABA inhibition is titrated to the symptoms.
I have not been addicted for 10+ years, I can drink whenever and however I want, but there is no physical dependence and I have no urge to drink, find myself going months without drinking without even noticing.
Also an ex smoker... I'll never smoke again... I am no longer a nicotine addict. I will not 'always be an addict'. There is no part of my life that has anything to do with tobacco or nicotine at all, it stinks, it's expense, I have no interest in ever smoking again.