David Bowie most likely had Aspergers Syndrome, and many of his songs and personas can be seen as an attempt to understand and reconcile his feelings of alienness. Indeed, Ziggy Stardust and the Man Who Fell to Earth are both aliens.
A Quorum user writes:
If he was autistic (and it seems likely, but I'll get to that), it's doubtful he was ever diagnosed. Most of the contemporary understanding - “awareness" - of autism, outside of old pathologized stereotypes, comes from autistic individuals diagnosed in the late ’80s through today. Meaning, the new broader understanding comes primarily from people diagnosed as children or young adults who have since shared their experience. Due to the time frame, this has mostly only happened in the past 10–15 years, as those children reached adulthood. Prior to that, there weren't enough of us to create the voice, and diagnostic awareness, there is today.
Bowie died in 2016. Unless he was diagnosed in his last few years of life, and likely by a young clinician with at that time brand new awareness of broader expressions of autism in individuals (beyond DSM pathologies), it seems unlikely it would've been recognized in him at all… he's of the era where he just would've been seen as “quirky" or “eccentric". I also imagine he had other medical issues he was more focused on in his last years, and let's be real - he was David Bowie, what's the point of an autism diagnosis? He owned his own island, he was doing fine.
That said, as an autiste myself, I do think he was autistic, and very much recognize autistic traits - my own and of friends - in him, to a startling degree. Notoriously “gender nonconforming" (a very common autistic trait, though still not well known to people not themselves autistic), prone to locking himself away for weeks and hyperfocusing on topics, generally had poor eye contact in interviews, seemed to fidget (stim) near constantly (at times joked about how prone he was to “fidgeting" when alone), seemed to be generally pleasant but with “interpretive" social rules (and challenged social norms and values incessantly, at times - according to him and those who knew him - without being fully aware of the extent), hyperlexic, as an actor/performer noted for sometimes being hyporeactive to things that would bother others, etc… His facial expressions, when not performing (read: acting), also seemed limited - he wavered between straight-faced and a big smile, little in between. Others have mentioned his apparent sociability, though it's worth noting some autistic people are very sociable (differences in social understanding don't inherently equal asocial tendencies - those are probably more often the result of trauma, a coping mechanism for being always misunderstood). And failing that, it's not a stretch to assume he was an expert at masking. Even his sociability is iffy, as it's well documented he'd isolate himself from other people for weeks/months at a time when younger, while hyperfixated on his latest interest. One could argue he was just “weird", but as advancements in recognition of autism have increased, it might also be safe to assume most of the “weird but not crazy" people of yesteryear were autistic, but diagnostic criteria hadn't caught up yet (that is, they were too “high functioning" - note quotes, please - to meet the slim definitions of yesteryear). It's also worth noting, regarding his shows of empathy to autistic children, that recent studies show we communicate with fellow autistics just fine, and are able to express empathy in mutually understood ways; our cognitive empathy is not limited with each other. not to mention the higher degree of affective empathy we (generally, but not always) possess.
I recall a story where, in the late ‘60s/early ‘70s, he bought a dress at a London shop, and wore it as much as he could. Someone called him some homophobic slur, and his response was, “well, I think I look pretty" and went on with his day. If that's not a textbook autistic response, I don't know what is.
