I used to be very dismissive of depression, like, "just go to Disneyland for a week" or "cheer-up we are on a rock in space, so why do you worry about x" levels of unhelpful.
Then a year or so ago I was hit by a string of stressful events, no fault of my own, that just mentally scared me, I went from being 24/7 chillaxed, to feeling constantly on edge, and it spirals so quickly, can go from having an okay week and having a weekend to look forward to, to having this cold chill run down my body and finding it incredibly hard just to get through the day, just this feeling of constant impending dread and hopelessness, and sometimes you sit back and realise your just not enjoying life anymore due to this, it saps the joy out of everything, so why bother.
I didn't even know it was depression until I was diagnosed, because it didn't fit my mental picture of depression just being people who are boring and have nothing to look forward to. The worst part is when you ignore the dread and have a nice day despite it, you then feel guilty about it, like your ignoring a problem you shouldn't be ignoring, it's so irrational and self-damaging, it's incredibly tough to live with.
don't worry, this isn't a cry for help, I have a good support network, and I've already lost a couple of people due to depression (and yes, in hindsight I feel super guilty for not understanding what they were going through), but it's taught me a couple of things the hard way, depression really isn't rational, and it's not something you have to "let" affect you, you really don't have a choice unfortunately. meds are also pretty shite and barely touch it, so love, compassion and patience are really important.
With celebs I figure they are often emotionally isolated too, like your partner is off filming a movie, and most of the people who you are surrounded by are not your family, or even friends, and probably people using you (agents, etc). Honestly, suffering from depression and being famous must be an incredibly difficult combination. I doubt I'd be here if it wasn't for being surrounded by people who genuinely love me.
I hope this person is at peace.