Richardson was suspended after testing positive for THC, a chemical found in marijuana, the US Anti-Doping Agency said on Friday.
Richardson secured her spot at this month’s Tokyo Olympics after winning the women’s 100-meter race at the US Olympic track and field trials in Eugene, Oregon, last month.
But her results were automatically disqualified because she tested positive for THC, and she will not be allowed to participate in her signature 100-meter race in Tokyo.
Richardson said in an interview with NBC’s “Today” show on Friday that she had used marijuana after finding out from a reporter that her biological mother had passed away.
“I was just thinking it would be a normal interview, and then on the interview to hear that information come from a complete stranger, it was definitely triggering, it was nerve-shocking because it’s like who are you to tell me that?,” the athlete said.
“From there just blinded by emotions, blinded by bad news, blinded by just hiding hurt, honestly for the fact that I can’t hide myself, so at least in some type of way, I was trying to hide my pain.”
Richardson said she wanted to take responsibility.
“I know what I did, I know what I’m supposed to do, I’m allowed not to do and I still made that decision. I’m not making an excuse or looking for any empathy in my case,” she said.
The World Anti-Doping Agency and the USADA label cannabis as a banned substance as it “poses a health risk to athletes, has the potential to enhance performance and violates the spirit of sport.”
After the suspension is up, Richardson said in the interview, she will “be back and able to compete, and every single time I step on the track I’ll be ready to compete for whatever anti-doping agency to come and get what it is that they need.”
CNN’s Aleks Klosok and Jill Martin contributed to reporting.