Xanax is outlawed in the UK because of it addictiveness. I hope they don't ban it here.
Actually, Xanax can and does cause cognitive problems. All benzos can. For one thing, evidence shows they interfere with the brain's ability to learn how to deal with stress. For others, there might be short-term memory loss. For others, no effect at all. But for most, the cognitive effects are only noticed when you stop taking the benzo, particularly after taking it a long time. That's one reason they are so hard to stop taking, and why in many countries now they are becoming very hard to obtain. But if you need it, you need it, and I'm personally glad the US still allows people to use them. It's just good to be aware of the costs as well as the benefits in case one needs to stop taking a med, which is when they can be most difficult. But then, so is this crazy disease.
Since it appears you only took Xanax on two occasions, it seems unlikely that you would have such a reaction. But it is not impossible. For some people a particular medication can act as a poison.
For an adrenal problem caused by inhaled steroids, I took very small doses of Xanax on an as-needed basis. Often I could do with as little as 1/2 of a .25 mg. pill. It worked well and I had no reaction, except that it aborted a panic attack. It never put me to sleep.
As a general practice, in order to avoid an untoward reaction (or to overmedicate myself), whenever I am given a medication, I try first a lower dosage than recommended. I often find that the lower dosage works well and I never have raise it. This is particularly important if the drug is addictive, which Xanax is. (Obviously I am not talking about antibiotics, when you have to take the full dosage.)
I have been taking xanax for about fifteen years. It has given me a normal life where before I was afraid of everything and having panic attacks. My mental capacities are equal too or greater than most of the people that I meat and or work with. It is true that it is addictive and if you don't need it you shouldn't ever start it. But for people like me it is a life saver and has made my life worth living. By the way my IQ by all tests that I have taken is over 130. I beleive the problem is that people who should't be taking xanax are taking it..I went through years of being diagnosed and trying lots of different medicines and xanax is the only one that worked. The doctors tried very hard to call it depression before they realized it was anxiety. I take two millagrams a day now and never need to up the dosage. But if I forget it I will have severe side effects. This is a small price to pay for giving me a life worth living. If you have problems with xanax it is probably not for you.
I hope you get this fixed up. Anyone can have an unusual reaction to a med, but doctors won't be able to tell you if the Xanax caused it or not, they'll only be able to examine you and determine if some bodily function isn't performing correctly. The chances of this being permanent are extremely unlikely, but I'd get to a doctor and see if something's wrong. As to the sleep issue, benzos are not a good sleep med. They actually interfere with normal sleep rhythms. Sedation is a side effect, not the purpose, which is to calm. Given your situation, which is trying to remedy a sleep cycle that's gotten way off, melatonin would be a better substance to try, as it is what the body naturally uses to set our body clocks. But first, get that check-up.
I am not sure if Xanax can cause permanent cognitive damage, but it would be my guess that if it did, it would be after years of daily use. If I am understanding your post correctly, you have only take a very small amount of Xanax. It would be normal when first beginning Xanax therapy to feel a bit "hung-over" the first few days until your body adjusted. What you are describing, not being able to think straight, finding it hard to form sentences and use certain terms that you never had problems with before, unable to study or do anything.............I think this warrants an immediate consult with your doctor. Unless you have had some extreme reaction to the Xanax, the amount you took would not do this to you.
It could all have to do with your messed up sleep patterns, the stress of school and your anxiety regarding the Xanax.
Only your doctor will be able to piece it together.
Peace
Greenlydia