Panic attacks are not at all necessarily repressed trauma. And while they may have multiple factors causing them, they can be precipitated by a single stressor. So sure, the kid could have started panicking in response to this one thing, if he was otherwise predisposed to panic/anxiety. (For that matter, do we know whether he'd ever had panics before for other reasons?)
Also, depression can be episodic, so while I agree that people don't generally go from catatonic to fine just like that, I wouldn't agree that it's not real life to recover from a depressive episode on one's own. Although of course the episodic nature of depression would also mean that depressive episodes would be expected to recur.
As for Teddy and Jo's therapy, I'd hope they were still going even if it's not referenced in the current episodes, but also, many therapies are relatively short-term and wouldn't be expected to still be ongoing. Those include effective treatments for PTSD and for major depression. I think both of them have plenty of reasons to be in ongoing therapy. But I also think it's not unrealistic that they could have completed treatments in this timeframe.
