Friend has memory problems but a clear mri? what could be the cause?

Mental Health: I am sorry, but an MRI is not in any way a effective or appropriate way to test for memory loss. Your friend needs to see a real doctor and have real neurological and memory testing done to include blood work, and mental health screening.

Many reasons: Medication adverse effect, lack of sleep, depression, use of alcohol or recreational drugs, low thyroid, B-12 deficiency, HIV, arthropod, or syphilis infections, elevated homocysteine, kidney or liver disease, poor brain blood flow due to carotid artery blocks, toxin or poison exposure, prior head injury. Have your doctor evaluate fully.

Not unusual: I have tons of patients who are severely demented and their MRI's look as good as mine would. There's nothing to guarantee an abnormal imaging study of any type in a person with memory issues. Need more information though. Are we talking a younger or older individual because that may change the type of problem we'd think about. Is it short term memory only or other things are off as well?

It depends: An MRI only looks for structural abnormalities. There are a multitude of reasons for memory problems that would not necessarily be detected. Age, medical problems, family history, medications and drug or alcohol use may contribute to the problem. There are games that can help with memory online and they are fairly easy to find. Search memory games. Have her ask her doctor for more information