I had stress related hair loss once, when I lost my mom. That whole month prior to her death was so stressful. I also had gone off the pill about a month prior to that, and that can cause it (hormonal). However, I saw 3 doctors about the hair loss over time- a general practitioner, a gynecologist, and a dermatologist, and they all told me confidently it was the stress. And I tend to believe them. That was the most stress and anxiety I've felt in my life, and that was a lesson at just how impactful stress is on our bodies. And my hair never went back to 100%. It's much better than when it happened, but it just never got back the same volume. I was told that it might never go back to normal - your growth phase can be disrupted to the extent it never gets back on track.