when did this behavior start and how was your relationship with your brother before?

how does he get along with other people (parents, friends, girlfriend?)

His behavior with you doesn't particularly suggest to me he is bipolar any more than the next guy. Unless there are other factors, to me, it is more suggestive of a 17 year old adjusting to his testosterone soup, and having a troubled relationship with his older sister.

You have suffered with a lot of depression and anxiety, Meg. Many of us who go through this find that those who do not experience it do not get it. sometimes, even specialists do not totally get it. Now you say you feel like he hates you - i suspect not, but you may be onto something else here:

A person can be overwhelmed by depression/anxiety in close family members - themoreso a teenager whose emotional experience is intensified by hormonal increase and flux. Not because they don't care but because they do... it can hurt very deeply, but they cannot control the situation, cannot improve the situation, and that can be intolerable. Some will put up a wall of defense - isolate themselves. Internally, emotionally. Rageful outbursts and unwillingness to be affectionate are not that "odd" in a 17 year old male. And these are also very effective "defense" behaviors if he needs to distance himself from you. This is not something he would be conscious of doing most likely, but more a defense mechanism against feeling someone too much for someone else. Your perception that he doesn't "care" may be right to the extent that he may in fact NEED to PREVENT himself from experiencing his feelings for you.

what do you think?

begs the questions though, of when this started, and how he gets along with others.

~ waves ~