Definitely not. I am certain of this which makes it even more puzzling. He doesn't have an addictive personality although does have mild OCD around tidiness and cleanliness, longstanding.
He doesn't have close friends but he admitted that a long standing band member who he's got a good relationship with had expressed some concerns about his drumming (in a nice way). Don't know about colleagues. His closest relationships are with me and my daughter and its like he's become a stranger to us.
Always some issues with communication which have become much worse though he's nowhere on autistic spectrum. Constantly interrupting and talking at rather than with when listening appropriate, picked up by my daughter's consultant other day, denial he's just said what he has, blocking communication and withdrawal at difficult times or when I'm upset about something. Argumentative and extremely intolerant even with the public these days. Nevertheless, overall he's been a kind and loving gentle person until recently. His sense of humour seems to have completely disappeared sadly.
Sorry, could there be some underlying reason for this sudden change.
Yes there could. While this could be a bipolar condition, medical conditions need to be ruled out.
This could be a low thyroid problem, a vitamin B12 and folate deficiency, even a brain tumor (although that isn't very likely).
Hopefully you can convince him to see a doctor and get an evaluation and testing