Question about my psyche

Maybe this doesn't fit here... oh well. I'll try.

Generally, I would say that I'm pretty mature. Sure, I like to have fun with my little sister (she's 15) and be a bit immature, but I'm still on a level I'd deem acceptable for a 20 year old. IF I'd be considered immature, it's nothing out of the ordinary.

Now, my big sister left the family in 2016 to live abroad for a year. When she came home, she moved in with her boyfriend and she hasn't been around a lot since. She is one year older than I am. When we were younger, she used to be very mean to me. I'd say she straight up bullied me between the ages of 5-16. I had to be close to her because we shared the same room most of the time but she used to hit me and say very hurtful things to me ("you're worthless", "you're ugly", "you're fat", "you don't deserve to live", "you should kill yourself" - the last one, she said when I was severely depressed and seriously contemplated committing suicide when I was 16 - etc. She said these kinds of things every single day).
She made me her "slave" - I read in one of my old journals yesterday and I wrote something like "I'm not at school today because I'm sick. I'm in the sofa watching the Vampire Diaries. Now my sister is telling me to make her a sandwich even though she knows that I'm sick and she's not. " I did a LOT of things for her because I was afraid that there would be consequences if I didn't. She threatened me with a lot of things like spitting on my pillow or things like that. She made fun of my self harm and threatened me with a knife. I was afraid of her but at the same time, I became very dependent on her as well and for a while, she was the only friend I had. I was jealous when she was with her friends because I had only her. It was a pretty ****ed up situation, really.

She came home today, and I instantly became very immature. Maybe on the level of a 12-13 year old. I can see on her that she gets annoyed with me, but I can't help myself. It's as though I literally become a 12 year old. I think it's really good that she went abroad because I could finally break free and become my own person. I also become very defensive of my own things - I don't want her to be near my things because i don't trust that she won't look through them... and now she's sleeping in my room. ;/

Anyway, do you think my current immaturity around my sister is a result of the torment I had to face from her during my childhood? Maybe they have nothing to do with each other, but it's just a thought that hit me today as it happened. I even pointed that out to my sister and she was like "but you're always like this" and I was like "yes, with you!" My mother agreed that I do "change personality" and become more immature when I'm around my big sister.

TL;DR: Is the bullying that my sister put me through between the ages of 5-16 the reason why I act like a 12 year old around her even though I'm 20?

Yeah I imagine it's related to the abuse. Like you regress as a defense mechanism.

That does sound right. You adapted to her bullying within that age range so it makes sense you'd take up those adaptions again around her. It's the way you learned to handle being around her.

What exactly does "becoming more immature" in those situations involve?

This might be a stupid question, but... can I really refer to it as "abuse"? I mean, it's hard to acknowledge and accept the fact that I've went through something like that. But I think that that's really what all my mental issues stem from - my depression before in my life, my low self-esteem, my inability to take initiatives in social settings making me unable to form relationships (although I have a friend that I got about 2 years ago so I mean, I can clearly do it, I just don't - and that relationship was formed through meeting each other every day for 3 years. It took a year before I started feeling even a little comfortable around her), my BDD-like symptoms... I've also struggled with OCD-like symptoms and extreme self hatred in general.

I wonder what my life had been like today if I hadn't gone through this. But I feel like I'm overreacting... I mean, it's my sister, for Christ's sake. Sibling chivalry is normal, is it not? Why has this affected me so much? I was never bullied/abused by my parents or people at school or anything.

Yes, I suppose...

It's literally as though I turn into a 12 year old, I'd say. I become annoying, obnoxious and loud (sorry not sorry). It's not like I turn into another person - I realise that I do this and can control myself if I want to, but that would require me thinking about it constantly. I do act like this sometimes with other people as well but I'm always like this with her. I have this thing where I speak sooo loudly without even noticing until people point it out. It has been quite embarrassing, sometimes, especially since I am usually so withdrawn and quiet in social settings (this happens when I'm around someone I'm comfortable with, aka my 2 sisters, mother and best friend).

I think when it's someone close to you it can be really difficult to frame their behaviour that way, and sometimes people don't mean to be abusive either but do emotionally abusive stuff because their own mental health is bad, but however you define it I'm sure the way she treated you contributed to your issues around her.

I think a lot of people have a poor relationship with their siblings. I seem to be a lot closer to my brother than most people are so my frame of reference is already skewed but never the less I still think regularly telling you you should kill yourself or hurt yourself is bound to mess you up and is pretty abusive.

Tbh it's stuff like this that makes me glad I didn't have a sister because some girls are really ****ed up like this. I hung out with a really terrible girl who kind of made my life a living hell when growing up but it would have been really awful if she was related to me. I did have a female cousin who I hung out with a lot and who wasn't terrible though. I'm glad that you have another sister at least.

It sounds like you know that's the cause of it and it sounds like you should trust your own judgement. Not having confidence in your judgement on that stuff especially can cause you a lot of problems in the future. You don't want to be in toxic relationships as an adult and accepting them because you experienced that stuff as a child and convinced yourself it was ok. Do whatever you have to do and believe whatever you need to protect yourself. And yeah, I would say that is clearly abusive, and sounds worse than typical sibling problems. Your sister probably has some issues too if she's doing that stuff to you and hopefully she will grow up or chill out or whatever to stop doing that to people. Even if you were just a sensitive person and needed more boundaries than a typical person to feel healthy, still you can choose who you want to be around and all of that too. But yeah, don't be afraid to admit that is abusive to yourself. Anyways, your sister definitely sounds a little on the ***** side, lol, but usually people like that are miserable i think so that might be something to keep in my mind too. anyway, i dont know your sister just guessing, she could have a personality disorder or something if she's behaving like that.

the size of your paragraph about your situation means you're smart and know about your issue a lot but you probably been hiding conflicted feelings thoughts without solution. So you're healing already it takes time to grow up and be independent, not isolated but trust yourself so that you dont become emotional and breakdown, defend yourself all you want but you need to have back up and this world doesnt promise anything. be optimistic.

I didnt read the whole thing but she sounds like an awful person sorry to hear.