EXCLUSIVE

Our sources say Lindsay has taken Adderall -- used to treat Attention-deficit/hyperactivity disorder and misused for various other purposes -- daily for years. She believes she needs it to function.
We're told Lindsay was steadfast -- either attach Adderall to the deal or she'd take her chances at trial. Sources say Lindsay's lawyer, Mark Heller, assured her he could find a lockdown rehab facility that would accommodate her demand.
Heller may not be able to deliver ... fact is, there's no such thing as a lockdown rehab facility that would take Lindsay, much less allow her to take the drug.
It's pretty ironic ... when Lindsay was jailed back in 2010, she got a doctor to prescribe Adderall while she was behind bars ... even though her ADHD diagnosis was called into serious question.
A number of people in Lindsay's life believe it was the Adderall that led to her downfall.