I'm at Columbia right now too - math major graduating next month - and I have pretty severe ADHD and what you're saying sounds like a lot of what I've dealt with over the last few years. I got bad grades in HS, enlisted, went to a CC after I got out, then transferred to GS.

I was in exactly the same position you're in about two years ago. I was in the middle of taking a little time off to handle some family matters and I had been really struggling in my higher level classes. I was extremely depressed and became convinced I was destined to fail and I should switch to a major that I was better suited for. I almost did, but I came to my senses and stuck with it for the better. ADHD is nasty like that and sometimes it's enough to make you desperate enough that you'll do almost anything to get your motivation back.

Columbia is also just a rough place to stay motivated for people in general (especially people dealing with issues like ours). The lack of school spirit or any sort of real community cohesion makes it really difficult to derive any meaningful drive from anything external. The administration also isn't particularly concerned with student wellbeing generally, but consideration for learning disabilities is fairly limited unless a professor is particularly understanding (which some are).

With classes coming to an end, I'd say get through the next few weeks then step back and make an honest assessment of the issues you're having and consider whether or not they're specific to Columbia, or if they're going to exist no matter where you go. Which isn't to say they're *your* issues, but they may be the result of combining ADHD with rigorous academics at an institution like Columbia.

Even if Columbia is the source of a decent proportion of your situation, consider that you've got one year left and that transferring will mean starting back at 60 credits (at most). So a summer off then finding a good therapist when you get back could be enough to hold you over for one more year.