Very common indeed, for reasons already addressed by others out here. It's a tough life for an aspie.
On top of Asperger's, I was professionally diagnosed with depression, anxiety, and ADHD. (Though I'm not 100% sure that last one wasn't a mistake in my case.)
When I was younger, before they knew about the Asperger's (I was diagnosed in my late teens), they called it "gifted with a sensory processing disorder." Which is true. But it's kind of leaving stuff out.
(As a side note, I find it curious that a lot of us seem to like and find comfort in labels, and seem to be okay with being open about it. In my opinion, that's a great way to fight the stigmas against mental illness and disability, but I've had a lot of people disagree with me and criticize me for it too...)
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"The important thing is not to stop questioning." -Albert Einstein