People who are your acquaintances often say that in passing as a way to sound friendly. But if they actually care about you and are a friend to you, they would email you back.
Emailing friends is acceptable, but only if they respond to emails. People who are younger (teens-20s) prefer to be messaged through text or on social media as a general rule. I use email if I want to write something long that would be too long for a text message, but if I want to chit-chat or plan something, I usually text.
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Given a “tentative” diagnosis as a child as I needed services at school for what was later correctly discovered to be a major anxiety disorder.
This misdiagnosis caused me significant stress, which lessened upon finding out the truth about myself from my current and past long-term therapists - that I am an anxious and highly sensitive person but do not have an autism spectrum disorder.
My diagnoses - social anxiety disorder and obsessive-compulsive disorder.
I’m no longer involved with the ASD world.