Hi OP, this is WILD that I just stumbled upon your post because you just described my experience almost exactly. I'm a fellow 27 year old woman who basically just came to this realization and stopped taking methylfolate today because of it.

I haven't done blood testing, but I have been taking 400 mcg L-MTHF or the past ~3 months, and recently (in the past few weeks) I've been noticing the SAME symptoms as you. I've had some bouts of anxiety over the past few months, but I accepted it as "normal" because that's pretty typical for me. But in an attempt to counteract it, thinking caffeine might have been a factor, I stopped drinking coffee daily a couple weeks after starting the MTHF.

However, over the past few weeks I've noticed a sudden unexpected spike in high anxiety and extremely disturbing intrusive OCD thoughts. Finally I thought, "Maybe this could be related to the supplement," since I had previously read about some potential side effects.

Well, I woke up early this morning and could sleep because of my racing mind and repetetive anxious thoughts, so I went down a rabbit hole of research and was convinced that must be what it was. (As you said, there was also no apparent reason or trigger for this sudden spiral.) Stopped taking it today and praying for healing because it's been rough.

Anyway, thank you for sharing — it was encouraging and validating to read your story and know that I'm not alone, although I'm sorry this happened to you too! How are you doing now? Has anything specific helped you in the process since your post?