Miller split with Grande in May and soon after, he was involved in a car accident, after which he was arrested for DUI and hit and run.
Shortly after the crash, ex-girlfriend Ariana Grande posted a statement about their former relationship, writing that she had "cared for him and tried to support his sobriety."
However, when discussing their breakup, Grande made it clear addiction was part of the reason for their split.
"I am not a babysitter or a mother and no woman should feel that they need to be," she wrote on Twitter. "I have cared for him and tried to support his sobriety and prayed for his balance for years (and always will of course) but shaming/blaming women for a man's inability to keep his s— together is a very major problem."
Grande announced her engagement to Pete Davidson in June.
Earlier this week, Miller spoke candidly about his trouble dealing with the pressures of fame.
Reflecting on the stresses of success, he said: "There's pressure. A lot of times in my life I've put this pressure to hold myself to the standard of whatever I thought I was supposed to be, or how I was supposed to be perceived.
"It's the job. This is what I signed up for. So, you just have to not. You have to have your own reality and that has to be the driving force of your life. Do I wish that every single thing I did when I was 19 wasn't a discussion? Sure."
Miller had just been preparing to embark on a U.S. tour.