my 2 yr old is defiant all the time, aggressive and has many bad habits...

my 2 yr old daughter is a smart energetic toddler, she speaks and comprehends just fine often she will scold you for something after she has been, but she doesnt ever change her behavior, she spits, bites, destroys things in the house from ripping curtains, to shredding paper, to smearing poop all over her room, to eating poop, she hits her 3 yr old sitter in the head with toys everyday, ive caught her sitting on top of her sister while shes sleeping hitting her...  im concerned that she has signs of more than just the start of add, my brother had asburgers add adhd as a child and he didnt do any of these things, he grew up and is now a masters student, but never exhibited any of these... im a stay at home mom, my husband works 70 hrs a week, we have a great home, i do hands on projects with the kids everyday like preeschool i dont know what to do with her im at my wits end...

[Sandman2]

    Well, they do call it the terrible two's for a reason.  And its much too early to label it ADHD etc.  
    What you do is you need to change her behavior.  Which means that you will have to be very consistent with her.   You also will have to watch her very closely for awhile and as soon as she starts the wrong behavior, you stop her and give her a very short timeout.   I would suggest posting over on the child behavior forum here - http://www.medhelp.org/forums/Child-Behavior/show/64. The members there have dealt with this type of thing before and have lots of good ideas.    Best wishes.

[Sandman2]

   Another idea for you.  I am just finishing a book called, "Raising Lions" by Joe Newman.  I think that you would find it very helpful.  Its worth checking out.  Best wishes!