Mental health (depression, anxiety) issues have been underlying problems with many addicts.
Quite so.
However, one LEARNS how to CHRONICALLY have mental health or mental ill-health, how to be chronically depressed and/or anxious.
And, probably one learns such the first 6 years of life from one's primary care givers.
DNA and hormonal personal differences can play a part. But the overwhelming part are the brain grooves and feedback loops that become deeply and intensely entrenched--as the OP article outlines.