yes depression is an illness. and it needs to be treated.
but - 'he needs to be the one asking' for help " because he is an adult. and a GP won't treat an adult unless the adult wants the treatment.
i went many times to my GP (same GP as my ex's) asking them to help him - to help his depression - the answer came back every time: "we cannot help him unless he asks us for help"
i know what you mean - but the OP cannot get him help - she can take him to GP, she can sit in the appointment, she can march him to the pharmacy for his prescription - as i did - but she cannot - just as i could not - make him take drugs or do therapy.... unless he is bad enough to be sectioned which he clearly is not.
i am not convinced that anger is a symptom of depression - or can be excused by depression . tho it may go alongside depression. it does fall to the OP to try and set the boundaries - "i understand you depressed but this behaviour and that behaviour is unacceptable" .
anger is anger. of course - it may be tied up with a period of depression.
but when my ex has been "on the floor" depressed - he has been very introverted/inward looking. not threatening or angry.
anger at himself/me/our dcs - and severe anxiety - to me that has been something else. on the descent into cannot-get- out-of-bed depression or the ascent into more manic state.... he got a diagnosis at one point of "depression with anxiety disorder" - the outwards anger/anxiety were seen as something co-morbid...
and of course everyone is different.
let's say he has underlying depression. sure it needs treating.
but even with that - he has shown he can be nice and can change his behaviour from being angry to being nice.
has he stopped being depressed?
no - because he continues to isolate himself.
so - logic says - the anger may not be directly a symptom of his depression - but may be something he can control... but yes -g et him to get help for his depression/anger issues - that is the starting point