"Teen Mom" star Amber Portwood had become so depressed in her rehab program she tried to overdose on pills -- and that's what drove her to quit drug treatment entirely ... entering prison instead.
A shackled Amber spoke with "Good Morning America" ... claiming, "I had taken 30 Suboxone [a drug used to treat opioid addictions] within 3 days. The depression took over. I would take 4 or 5 at a time."
Amber said, "I felt like I'd rather do my time and get it over with, and make the best of a situation that's been handed to me." Amber was sentenced to five years earlier this week.
She added, "I'm not just going to sit. I'm going to do substance abuse classes. I'm going to get my GED."
Still doesn't make any sense -- Amber had been given the opportunity to receive out-patient drug treatment ... WITHOUT PRISON ... but she chose prison anyway.