The 24-year-old actor and comedian responded on Instagram Stories after fans suggested his borderline personality disorder makes his romantic relationships toxic.
"normally I wouldn't comment on something like this ... but i been hearing a lot of 'people with bpd can't be in relationships' talk. i just wanna let you know that's not true," Davidson wrote.
"just because someone has a mental illness does not mean they can't be happy and in a relationship. it also doesn't mean that person makes the relationship toxic," he said. "everybody is different and there are a lot of treatments for mental illnesses and i have done/am doing all of them."
"im simply writing this because i want everyone out there who has an illness to know that it's not true," the star added. "mental illness is not a joke it's a real thing ... for all those struggling i want you to know that i love you and i understand you and it is going to be okay."
The Saturday Night Live star was first linked to Grande this week following the singer's split from Mac Miller.
"It just started and is casual," a source told E! News.
"Ariana was holding Mac together for a long time and it wasn't a good relationship for her," the insider added. "She is in a very good place and very happy now."
Davidson went public with his struggle with borderline personality disorder in an interview with the WTF with Marc Maron podcast in September. He was diagnosed with the disorder in 2017 following a stay in rehab.
"It is working, slowly but surely," the star said. "This has been the worst year of my life, getting diagnosed with this and trying to figure out how to learn with this and live with this."