What does Adderall XR do?

I've been prescribed Adderall XR, and I'm nervous about it. First of all, I'm somewhat ashamed that I'd have to take a drug. I'm willing to work on that. But I'm also worried about what the drug does to me and if I need it. When I take it, I feel energized and awake, and I can really focus on things, and I feel way more interested in things. What are the expected effects on ADD and non ADD people?

Also, how is amphetamine different from amphetamine? I want proof (in the form of multiple long-term studies) that Adderall XR won't give me brain damage or other problems.

These are very important issues in my life. Please let me know anything you know. Thanks

This is probably not the best place to seek expert advice. The responses you'll get here will either be based on personal experience, or folks will post stuff they found on the Internet--the same stuff, in other words, that you could find yourself.

In your place, I'd start by talking to my doctor and insisting on some answers. If I wanted to get my hands on multiple long-term studies I'd go to the nearest college or university with a decent hard sciences program and ask the librarian to help me locate the studies--if they exist. (Amphetamines have been used for over 50 years, so I'm sure you'll find some long-term studies, but I doubt very much you'll see anything long-term that specifically addresses Adderall XR since this is a relatively new drug.)

Here's the little bit I do know:
Adderall is a stimulant, and Adderall XR is a form that's designed to reduce the number of dosages you need to take--usually reduces from twice daily with Adderall to once daily with Adderall XR. Like all stimulants, it increases the amount of certain chemicals in the body, thereby stimulating the central nervous system. This is intended to help you concentrate. (We know that it works, but like most meds, we don't know exactly how and why it does so.)

I hope you find what you're looking for. Don't be afraid to press your doctor for answers.

Could Adderall make you nervous, anxious, or increase attention on negative feelings, possibly fueling the elaboration of negative tendancies and thought patterns?

Basically, I don't know if I need Adderall, and I want to know if some negative experiences I'm having lately are related.

Addrall's a powerful stimulant, if you find that you are nervous, anxious or depressed a bit too much after they've worn off the normal effects of euphoria and concetration, then slow down on them and lower the dose. So to your question is yes all of that can be explained for the residual effects of any stimulant will cause insomnia, anxiety or depression. But don't fight back with more because that will only lead to abuse and:

Too much makes you psychotic over a period of time.

Don't let the drugs abuse you more then it.