I have a really good friend that I think is suffering from some kind of mental illness. I am not sure if it is relating to dementia however. He is just not himself these days. He is not on any HIV treatment plan and has been positive for at least 12 years. I do not know what his counts are exactly but I know they are not good and he has been on every combination of meds possible. He acts like a totally different person. He is beligerent at times, suffers short-term memory loss, paranoid, and sometimes doesn't make sense when he talks (like his ideas run together and he cannot make sense of his thoughts and feelings, he also keeps himself isolated from friends and relatives both physically and emotionally. Could this be dementia??

Yes, it very well could. The typical symptoms include short-term memory loss, slowing of thinking, social withdrawal. Some people also develop difficulties with paranoia and agitation.

Progressive symptoms of HIV-associated dementia usually occur in those who have failing immunity, low CD4 count and high viral load. Your friend's best option is to get back on an effective HAART regimen.