For a lot of kids, there is still a lot of mental maturity happening up until age 26, along with mental health changes also often occurring at this time. It’s so tough.
Strictly speaking (ie. taking a moment to set aside your family’s salient medical history), there have always been students that haven’t successfully navigated the switch to more rigorous academics. Having complete freedom on their own to meet or not meet greater academic challenges is a somewhat new experience. In high school, it’s a smaller space and teachers/kids can see in class who is and isn’t around. Post-secondary, that is no longer the case.
If he is still at school, who can he access that can help be an academic “accountability peer” for him? Doing well in school subjects (the academics proper) is an entirely separate thing from doing well in the managing of coursework scheduling (finding the time to do homework, study, and prep work needed to get passing grades).
He was thrown into the deep end; perhaps he was shocked by not knowing what to do and retreated (had an episode in high school already, so there is a bit of a pattern).
The key here seems to be getting behind in a class and not seeking help. One missed class can start a cascade effect, and things progress rapidly.
Personal trainers are used to be accountable to fitness goals; perhaps your son could really benefit from a tutor for academic success. (Meeting a few times a week, and the tutor comes to him to start? Otherwise it’s something else he can try to blow off. Unfortunately, in his case, the large setting makes it easy for him to retreat, which will only increase his anxiety.)
Forming healthy habits aren’t always just physical ones, but mental ones. This is especially important for people who suffer from depression.
If he hasn’t left school yet and doesn’t want to leave his friends, someone to help him through the day-to-day organizational/emotional difficulties of being in a mess is crucial. If/when he does leave, then things are in place (medical withdrawal, leaving school on terms that doesn’t increase the damage to him down the road). Many kids need this organizational help when they head to college (especially on the quarter system, which is perhaps a harder system for your son to navigate than a semestered one due to the speed involved).
Getting work done and feeling better about himself is a good sign; but other posters have spoken about this in the context of larger concerns that must be addressed.
Obviously his mental needs require greater guidance. So sorry he is overwhelmed. And this post is not meant to negate what has previously been said by posters experienced in this matter.