Natsuhi's are brought up in canon frequently and she takes a ton of unknown meds for them. Normally, to bully her with 'oh you're not feeling well, pull yourself together. Get over it. '
They're a combo of
-genetics, her mom had them
-stress
-trauma

Then magical bullshit adds, invisible witch following her and smacking her in the back of the head and.... contact with ancient demon/god because preists and the headaches are her price

It's wild to think about how much mental health care has changed. Even in just the last 20 years...haha ;-;