Simone Biles' ADHD medication is banned in Japan, but a Tokyo 2020 exemption allowed them for athletes

• Simone Biles withdrew from both Olympic all-around finals over mental-health concerns.
• The superstar gymnast later said she was experiencing "the twisties," which cause disorientation.
• She takes ADHD medication that is not permitted in Japan, but an exemption likely allowed her to bring it.

Simone Biles has been struggling with her mental health in Tokyo, which prompted the superstar gymnast to pull out of both Olympic all-around finals.

The withdrawal of the biggest star at this summer's games was a shocking development that birthed a worldwide discussion about mental health awareness and management. But it also gave rise to some questions, including what sparked Biles' case of "the twisties."

Some have suggested that Biles' ADHD could be to blame - and it's a reasonable assumption given Japan's ban of most medicines commonly used to treat the disorder in the US. But Biles and other Olympic athletes may have benefitted from an exception to the rule.

"A special arrangement is in place specifically for the Tokyo 2020 Olympic and Paralympic Games to allow athletes taking these medicines for therapeutic use, and with an approved Therapeutic Use Exemption, to import personal supplies for the treatment of their medical condition while they are in Japan," a document provided via Team USA says.

Athletes were permitted to "apply for permission" to bring otherwise banned drugs with them to Tokyo. This applies mostly to dextroamphetamine - or Adderall - and other stimulant drugs, but it doesn't appear this applies to Biles' regimen.

An illegal release of some high-profile athletes' medical data in 2016 showed Biles had tested positive for methylphenidate - the official name for Ritalin, another common medication for the treatment of ADHD. The situation led the then-19-year-old star to publicly address her ADHD diagnosis and say she's taken the medication since she was a child to manage her symptoms.

"Having ADHD, and taking medicine for it is nothing to be ashamed of," Biles tweeted at the time. "Nothing that I'm afraid to let people know."

Ahead of the 2016 Rio Olympics, Biles filed for a "therapeutic use exemption" through the World Anti-Doping Agency, which enabled her to continue taking the drug throughout her breakout competition.

While the laws in Japan are extremely stringent when it comes to stimulants, they're slightly more lax about psychotropics, the class of drugs under which Ritalin is categorized. Athletes and nonathletes alike can apply for a Yakkan Shoumei - an "import certificate" allowing for the import of some otherwise prohibited drugs - that permits them to bring up to 2.16g of their methylphenidate into the country.

If she filled out and submitted a Yakkan Shoumei, Biles was covered to continue taking Ritalin in Tokyo without fear of arrest. So while it's impossible to determine what has caused Biles' case of "the twisties," a lack of medication is almost certainly not to blame.

Biles is still eligible for the remaining four women's artistic gymnastics events in Tokyo, though it remains unclear whether she'll participate. Her next chance to get back into the gym is on Sunday for the vault final. The balance beam, floor, and uneven bars finals - all of which Biles has qualified for - will take place later in the week.

A previous version of this article suggested that Biles may not have been able to bring her ADHD medication to Japan. It has been updated to reflect information provided via Team USA and additional sources.