Luna was diagnosed with early onset schizoaffective disorder, depressive type, after her mother passed away and she had her first psychotic episode, and then a little after fell into a depressive spell.
Many of her ‘odd’ behaviors are actually magical treatments for hallucinations, delusions and disorganized thinking, as well as little tricks to lessen the symptoms of her depression.
For example, dirigible plums help lessen the effects of disorganized thinking, and wearing them in her ears helps even more than eating them, and her butterbeer cork necklace is a lucky charm to help reduce anxiety around hallucinations and delusions.
She also keeps her wand tucked behind her ear because of a belief that she could die from a backfiring curse, like her mother, without her holding it, thus keeping it tucked where it can’t hit her, unlike most the wizarding population, who keep it in their pockets.
I think one thing that I personally find really refreshing (well, maybe not refreshing…real?) about these post-lily-pad updates is that there have been a number of characters that confront the onset of mental illness that turns out to be basically part of who they are…Terezi and Dirk come to mind mostly, but it’s this sort of growing-up-means-growing-somber, a sort of resignation to some mildly inescapable fate of “dealing with” yourself
And it’s not like, the end of the world for either of them–it’s something they realize, confront, and quietly acknowledge as something they’re going to have to work on, even if it’s not necessarily going to go away. It’s not this deeply tragic, terribly dramatic thing, it’s just…a heaviness. A burden to carry, but one that, with support and self-care and honest reflection, can be carried. It’s not something that happened to them or some painful backstory or the world falling around them…and it’s also not something they ignore or repress from themselves (at least not in this iteration). But it is a truth, and it is difficult, and it does create a fragility in otherwise very strong characters
And that’s not something that a lot of media shows well