I don't identify with any of the characters I'm discussing. If I did, it would probably be Emma. I don't identify with any of the women or girls on the show. But of anybody, what goes on with Emma with her obsessive-compulsive disorder, anxiety, and panic attacks is quite clear to me. I saw one blogger say that Emma's panic attack about the wedding, the panic attack where Finn kissed her at the end, was triggering to her. Now that I think about it, it's odd that I didn't really react to that scene with any identification. I watched, I was aware of what was happening, but I wasn't there with her.
I watch her obsessions and compulsions, and I understand what's going on, but I don't have an emotional reaction. I don't seem to have a trigger for it when it's Emma. She's a character, it's fiction. Yes, people feel that way in real life, but that's real life. I'm at a distance from her. I suppose that's also odd, but that's my feeling -- or lack of feeling.
I'll look at Artie's disability and mobility aid next. I've never experienced paralysis, but I'm familiar with wheelchairs. I worked as an assisted-living nursing aide in retirement communities off and on for nine years. I know about mobility impairments and accessibility. I went between using a walker and a wheelchair for a few months when I broke my ankle badly. Grandma S. used a wheelchair in her last few years. I know about transferring someone else and transferring myself, helping people bathe, using a shower chair myself -- I have experience with those things. I've read autobiographies of people with various levels of paralysis and books that describe the medical aspects of injuries to vertebrae and the spinal cord. So no firsthand experience with that, but some secondhand experience.
McKinley is for the first couple of seasons shown to be a place where you're considered a boy if you're capable of violence. Things gradually changed. Artie was eventually accepted as a bro. Artie was always shown to have a mind of his own. Artie wasn't thought of as gay for joining a glee club like the other male characters were because it wasn't thought he had a sexuality, but he quickly enough established his interest in women. I'd had years and years of interacting with people who used wheelchairs, so I think I was past a lot of the characters at McKinley in my attitudes.
One of the recurring disabled characters introduced fairly early on was Becky. Mom worked at a school for children with intellectual disabilites, including children with Down Syndrome, for a few years when I was a child, and she'd bring me along every so often. The school was part of the county Intermediate Unit. Later I read a number of books about Down Syndrome. I hadn't had much direct interaction with individuals, so I think I was about on Will's level in my thoughts about Becky. She was introduced in "Wheels" with Brittany helping her with money, which gave me the impression that her intellectual disability was moderate. (That's probably an outdated term for classification.)
Becky did everything Sue asked of her, which led me to believe that she was obeying without full comprehension of what Sue was doing. It wasn't until she did a voiceover in Received Pronunciation that I realized she was understanding much more than I'd thought she was.
Arguably, Brittany has an intellectual disability. She's quite verbal, though, and that will cover up a lot. At the time I watched the first season and first half of the second season of Glee on DVD, I was living with a brain-damaged roommate. R.A. was quite intelligent and very verbal. She couldn't handle money and couldn't do laundry herself. R.A. covered up some deficits to a degree, while others were plain. Sometimes it was hard to tell what was brain damage and what was psychiatric, but I'm pretty sure the difficulty with handling money was the brain damage. The math skills were just not there. She had problems with executive function, though I'm one to talk.
Brittany is described as living in a magical world of her own. I put it that her version of what was going on wasn't the consensual reality that Kurt, Artie and Santana had. I've also seen it argued that her comprehension on certain subjects is better than the other characters believe, and better than much of the audience believes. I have a hard time telling, but I'm willing to believe that she understands some things that the other characters think she doesn't.
Sam and Ryder have dyslexia. That's a relatively straightforward learning disability, from my understanding of it. Ryder seems to be in the same consensual reality most of the other kids are. Sam varies a little, but generally he fits in as one of the bros.
I'm sure I'm forgetting people. I'll add more if I think of other things.
Added: It occurred to me that there were things once considered mental illnesses that are not considered so anymore. In the 1950s and 1960s there were books like Homosexuality: Disease or Way of Life? The author of that one concluded that disease was the answer. Homosexuality was classified as a mental illness until 1973. I think it was the American Psychiatric Association that decided that year that it wasn't. Dr. Evelyn Hooker was a leader in getting that changed. There are still psychiatrists and therapists who tell people (or their parents) that they can be "cured." Those psychiatrists and therapists are considered far out of the mainstream now, and harmful. I believe they get thrown out of mainstream professional organizations now. Finn told Artie, "Being gay isn't a handicap." That awareness had even reached fictional Lima, Ohio.