My friend is a poor methylator [0], which means she can't turn the provitamin food fortification folic acid into Vitamin B-9. The prescription drug Deplin is a form of Vitamin B-9 that is approved as an add-on therapy, for when 'antidepressants don't work'. AFAIK, people who are poor methylators say they do better when they avoid folic acid.
[0] https://news.ycombinator.com/item?id=30334122
I have commented before about my efforts to help my friend get appropriate treatment. My latest filing, a petition for rehearing, has been distributed to the Justices of the Supreme Court of the United States [1]. Hopefully they'll talk about it at their conference on April 14 2022.
[1] https://news.ycombinator.com/item?id=30884187
Sometimes people benefit from the SSRIs' allepregnanolone boost [2].