Rebecca was emotionally abused by her mother, and her father abandoned her. They're both terrible, but she does the work to make her mental health better throughout the show.
The main storyline initially focuses on Rebecca running into a man she briefly dated in high school, dropping everything, and moving across the country to pursue him. As she attends therapy, she realizes she needs to own up to this and offers a sincere apology. There is also a subplot where Rebecca is stalked by a former college classmate.
Protagonist has a history of childhood abuse/neglect (primarily emotional) that is a major focus of the storyline. There are some brief flashbacks to her mother yelling at her as a child.
Alluded to in the song “Nothing Is Every Anyone’s Fault” but it’s not clear if it’s actually true and even then the song is clearly making fun of the flimsy excuses some people to justify bad behavior
Protagonist takes a random pill she finds on the floor and smokes weed (S1E7). Two characters unknowingly take drugs at a music festival (S2E5). A character finds out a loved one is drugging her with anti-anxiety medications in a very misguided attempt to help her (S3E5).
A pet starfish is neglected to the point that it starves to death, and its deceased body is shown. Dialogue reveals that a character has killed several other pets this way and considers it no big deal, but asks that no one tell the pets’ previous owner about the mistreatment.
As mentioned by a previous commenter, a starfish is killed through neglect, her body is shown floating in her tank, and it is indicated that several others have been killed as well.
"In one episode, a character discusses how she had a sexual relationship with her teacher when she was in high school.
It was apparently consensual and the character claims it was no big deal, but another character is highly disturbed by this, pointing out that it was statutory rape and asking if the teacher was ever fired." from Unconsenting Media
In season 3 Rebecca’s mum crushes up anti anxiety pills and gets Rebecca to take them by hiding them in milkshakes she is making for her. This is out of concern for her mental health but Rebecca is upset when she finds out.
A minor character is hit by a bus and shown in a full body cast. The same character later falls off a building (though there is no depiction of him hitting the ground) and is again shown in a full body cast.
A major character is depicted almost falling into a hole dug for construction/maintenance but is saved (S3E4). A minor character is pushed off a building and injured, but he isn't depicted hitting the ground and is later revealed to be alive (S3E13). An unnamed character jumps out a window during a musical number, and it is unclear if he is dead/injured (S4E3).
In the beginning of season 2, though her boyfriend falls of the face of the earth. Also near the end of season 3. It is stated as wrong, though, and these things don't last.
S1E1: "Anyway, I gotta go. Today the dermatologist is telling me if it's Cancer."
S1E9: Episode begins with Rebecca watching a movie called 'The Cancer Crew'.
S3E5: "For once I don't want her to have a cancerous mole."
[MAJOR SPOILER] It is revealed in a flashback that a character who committed a serious crime was ordered to receive treatment at a psychiatric institution in lieu of a prison sentence (S2E13). Another scene involves an individual's hospitalization (presumably in a psychiatric ward) after a suicide attempt (S3E6). This individual later begins outpatient treatment with a staff psychiatrist.
Verbally violent— it’s called splitting and the main character attacks her friends verbally in a rage/response to emotional distress.
She also threatens her boss with a pen, chases and tackles him (but it’s not violent-violent).
Also it’s honestly ambiguous whether the songs are actually literally happening or only in Rebecca’s head. Kind of a, “is Hobbes in Calvin and Hobbes just a stuffed animal or a real physical tiger because there’s honestly evidence for both” kind of situation
No cutting depicted. Protagonist engages in a variety of self-destructive behaviors including binge drinking, drug use, reckless sexual encounters, etc.
The protagonist Rebecca makes a suicide attempt onscreen. Nathan’s mother made a suicide attempt before the events of the show. Before Rebecca’s suicide attempt, her mother catches her researching suicide methods on the Internet
Someone in the pilot tells Rebecca she doesn't look Jewish. As noted above there's a lot of jokes about being Jewish but it's mostly tongue in cheek since Rachel Bloom is Jewish and often incorporates it into her comedy.
A lot of "I'm so stupid" and S1E3: "I have friends song" there are people with burns, scars, etc in the group of ppl with no friends- but could also be seen as empowering & a call out to abled people (not sure) ?
Note that many of the comments about fatness come from characters who are self-deprecating or from characters known to be emotionally abusive, rarely is fatphobia shown in a positive light.
It is revealed that Rebecca previously had a relationship with her married law professor.
We don't know exactly how old each character was but at the start of the series Rebecca is 26 and we can assume the age gap between her and her professor was significant.
There is sexual content that isn't too graphic. Some I remember:
S1, E17: During the song "oh my god, I think I like you" there are sex scenes.
S2, E1: mentioned but not graphic
S3, E2: the song "strip away my conscious" shows a character undressing themselves to trade sex for getting revenge (doesn't happen)
No, but the main characters relationship with her father is often directly compared to her romantic relationship with men.
In the song: "Maybe she's not such a heinous bitch after all" there's a line that goes:
" I know it sounds like I'm falling in love.
Well when we're findin' a mate, it's our parents we're thinkin' of".
There is also a song in the first season that is called "I love my daughter (but not in a creepy way)" where a father is afraid of his affection appearing as such.
Nathan cries a few times throughout the series. He tries to cover it up each time because he has internalized from his father that basic human activities like crying and napping are weak and unmanly
Rebecca gets diagnosed with Borderline Personality Disorder (BPD)
Note: Not technically an illness but has definitely had a chronic impact on her life. With the right treatment BPD can improve to the point that some patients almost completely eliminated however it is not considered to be "curable". Treatment for BPD can be extremely successful and have a massive positive impact on peoples lives however it takes a lot of hard work and effort.
A minor character is implied to be homeless in s1e5 and asks the main character for money, she is addressed rudely by the MC but she later returns and is treated very kindly.
The song “Thought Bubbles” involves a character referencing how they almost let a kid drown while working as a lifeguard due to being unqualified. Nothing is shown.