I think it depends entirely on the situation. I think I fall into a strange category in that I should have been diagnosed as a child. I'm HF, but not as much it seems as most of the women who fall through the cracks (I was homeschooled, my parents have recently told me they worked out I was on the spectrum but 'didn't think it was relevant'/thought I'd be offended), so my whole life people have treated me weird anyway. I feel as though having a name for it has been really helpful for people around me because they have a reason for all the weird. I can definitely see why a lot of my behaviour had confused them previously, and I'd hurt a lot of people unwittingly because when my capacity to cope reduces I withdraw from any human contact for months at a time as much as possible.
My family are the only ones who have been unhelpful about it, and that mostly because I'm pretty upset at them for all knowing what was going on, talking about it without me and failing to share a) that they recognised there was anything going on b) let that follow through to any kind of empathy. They still like to see autism as a chronic overreaction to everything.
I tend not to just share it as a label though. I say the diagnosis, followed by what's relevant to the situation. i.e. '...which means that I find x situation difficult for y reason...". As much as possible, I try to plan ahead for these kinds of explanations, because in the moment it rarely comes out the right way up.
I do think people have patronised me more than before, but it's only been a few months so we'll see if that gets better or worse. The few people that really matter have really taken on board how they can get alongside me and help.
I find people don't understand aspergers/autism at all in the general public. They can identify some of my behaviour as such (the annoying things for them), but don't see the whole picture or understand at all why those things happen or see the iceberg under the surface of those behaviours). e.g. my Dad sees the label as just clarifying how I need to try harder to hide it, and he thinks it'll give me hints for hiding it better - zero empathy for the fact that those difficulties are the underlying chaos breaking out into the open. My husband has a friend and he and his wife have been so amazing. Especially giving my husband someone to talk to, and I feel like they've tried really hard to understand it. A click moment came for them when I said to them that all of the weird body movements if I'm really stressed and all that stuff are just like tiny bits of the intensity inside my head breaking out of my body, and that most of my energy goes into trying to make all of that less, but that means I have nothing left to do all the things other people are expecting me to do. They've been really patient in giving me time to get things out and say what I need to say without talking over me because of that explanation.
The only medical professional who has been notified about it (my GP) has been excellent about it. I don't know whether I would tell others. I find medical professionals dismiss and patronise me anyway unless they know me, so I can't see how it could really be much worse.
I guess the tl;dr verson would be: I think it's helpful when it is linked to a specific, concrete context or outcome and makes it clear to the other person why your behaviour is different and how they can help. If they aren't trying to help before the explanation, I doubt they'll try help afterwards.
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Diagnosed ASD
AQ: 42 (Scores in the 33-50 range indicate significant Austistic traits)
RAADS-R: 165
RDOS: Your neurodiverse (Aspie) score: 159 of 200
Your neurotypical (non-autistic) score: 44 of 200
You are very likely neurodiverse (Aspie)