Mother is out of control

I recently moved back home with my family (mom, dad, and two sisters) Things have been extremely rough. My parents marriage is a disaster (my dad has his own issues) but my mom attacks him verbally and physically. She is in a rage every night. Over small things....things that would never usually bother anyone else. She calls everyone in the family awful vile names for absolutely no normal reason (just for dropping a crumb for instance) She screams and yells and tries to control everyone and everything. She is extremely violent and unstable. She throws things, breaks things and attacks different members of my family. She always complains and never has anything positive to say, ever. It never used to be like this but over the years it has gotten worse. Sometimes I can't even sleep because she wakes up randomly just to cause a problem. It's gotten really out of hand. I moved in to get my personal finances together and moving out only means leaving my scared 11 year sister in a bad situation. Also, my mom holds a very important job that she is actually really good at (she is a different person at work) and she could lose the job if she does anything remotely illegal. I am really at a loss. I would say 90% of the time she is angry, depressed, crying, yelling, and causing an uproar and 10% of the time at home she is quiet and calm. She doesn't think she has any problems and puts blame on everyone else. So I dk know how to get her help. She says and does things ( verbal and physical attacks) and either lies about it later, defends her place or doesn't even realize she is doing it. Its insane. Its causing a very hostile home environment. Is this a mental disorder specifically? Is this just symptoms of depression? She used to be on antidepressants years ago but stopped taking them and refuses to go back. She wants the whole world to change before she does:) I love my mom but she is not the person she used to be, Any advice would be greatly appreciated.

[j17c27]

WOW...reading this reminds me exactly of my family..except the roles are switched.  My dad is a piece of **** and my mom is the sane one.  Like really, everything you described is EXACTLY what goes on at my house.  It recently has been getting really really rough.  I cant get through a day at my house without smoking pot or drinking cause this house is the worst place to be cause of my dad and I cant handle it sober.  I get SO confused becuase i dont know if I should hate my father becase of how horribly he treats my mom, or love him cause i mean...he is my dad and i guess I almost feel sorry for him.  He also is a complete drug addict/alchoholic.  Once in a while we will have like a good conversation or something...and then it makes me really like him, but then the next second he will flip out at my mom for no real reason.  He has made my mom suicidal...and she tells me everyday how much she hates him and how she wants to die.  It really freaks me out.  im 17 and going to college next year, so im moving out.  I have a little brother who is 13 and Im so worried about him.  
So know that you arent alone...this is a truely awful situation to be in.  Has your mom considered therapy? Having someone to talk to can make all the difference in the world.  My dad refuses therapy...and my mom really should go to therapy so she doesnt vent to me how much she hates me dad (it really makes me depressed).  Therapy can be very helpful.