Morrissey has never said this as far as I know. He is of a generation where it is common for those that have it to not know. Even if he has it and knows about it he has a right not to disclose and we need to respect that. Morrissey does not strike me as a person that would make a public cause out of his condition if it exists.
Musicians exhibit spectrum traits hyper focus , special interests, eccentricity etc. But they have to preform with strong lighting, do a lot of marketing and networking.
Morrissey became and still is an icon to people who feel like outcasts for whatever reason. That is more then enough.
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“Self Acceptance is a process not a performance”
“You are autistic enough. And you always have been”
Professionally Identified and joined WP August 26, 2013
DSM 5: Autism Spectrum Disorder, DSM IV: Aspergers Moderate Severity.