MINNEAPOLIS — Some doctors in the Twin Cities are concerned that a growing number of young adults seem to be faking attention deficit hyperactivity disorder in order to obtain the prescription stimulant Adderall.

University of Minnesota student Christopher Meyer said legal and illegal use of stimulants has become common at the university.

Hennepin County Medical Center neuropsychologist Paul Marshall authored a study that says the unwarranted use of Adderall is contributing to a shortage of the drug. Marshall has developed a tougher screening test for symptoms and says it should be given to all ADHD patients.

The National Institute of Mental Health said the number of adults in the U.S. who actually have ADHD is less than 5 percent.