How can you tell if a bald spot in your hair will never grow again ?

Just wondering if anyone call tell if the hair on your head will ever grow back, if it has been thinning ?

I have hair thinning on both of my temples, but it’s not completely bald. I still have some baby hairs there, and this doctor told me that my hair will grow back again.

But the skin looks smooth and I don’t really see any new hairs popping out, does this mean that the hair will never grow out again ?

I know it’s going to take time for my hair to come back, if it does, I was just wondering if there are signs that it wouldn’t grow again.

Note – The hair has been thinning over time, for about 1 year. I’ve been really stressed out, and they found nothing abnormal with me medically, so the doctor thinks it’s all from being stressed out.