A new survey suggests that almost 25 percent of adults who seek medical treatment for attention deficit hyperactivity disorder (ADHD) are exaggerating or faking symptoms, to get their hands on stimulant medication such as Ritalin or Adderall.

MSNBC reports that the survey of 268 patients found that 22 percent of adults who said they suffered from ADHD either didn’t have the disorder at all or tried to make their symptoms appear worse. Lead author Paul Marshall, who reported his findings in the journal The Clinical Neuropsychologist, said that some students want access to ADHD medication to help their concentration and focus, while others use it to get high. He used patient interviews and questionnaires that were designed to catch people who might be faking or exaggerating symptoms.

The article explains that ADHD medications appear to stimulate the brain, increasing levels of chemicals associated with attention and behavior. The drugs have a calming effect on people with ADHD but can be dangerous in people without the disorder, the article notes.