This is the exact opposite to what happened to me. I went from more straight on top layers (curly underneath) in my youth, to much curlier in my middle-age. If I let it air dry now, it's ultra curly. I never knew why such a change happened. I have the curliest hair now of anyone in my family. As if I am some oddball. I sometimes joke it was the ECT, but it changed even later than that. I still haven't gone through menopause, even at 50, so don't know if anything hormonal played a part.

I did have some quick shedding of my hair, at one point, from Lithium, back 7 years ago. That could have started the transition, but the bulk of hair came back. I have a big mop again, but really curly hair makes it seem bulkier.