Before she became famous, Fergie fought drug addiction, and in a new interview with Britain's iNews, the singer opened up about her worst experiences with crystal meth.

"At my lowest point, I was [suffering from] chemically-induced psychosis and dementia," she recalled. "I was hallucinating on a daily basis. It took a year after getting off that drug for the chemicals in my brain to settle so that I stopped seeing things. I’d just be sitting there, seeing a random bee or bunny."

Fergie's hallucinations were extreme: On certain occasions, she told iNews, she believed government agencies including the CIA and FBI were pursuing her. In a prior interview with Marie Claire, Fergie explained how her meth-induced paranoia drove her to paint all her windows black. That way, the "FBI" couldn't keep watch on her. Realizing that the SWAT teams in her brain weren't reality, but rather a result of drug abuse, was "freeing," she said in the interview. The former Black Eyed Peas singer once classified meth addiction as "the hardest boyfriend I ever had to break up with."

Related: Fergie Just Opened Up About Her Wild Sex Life With Josh Duhamel

Meth has been around since 1919, but crystal meth—d-methamphetamine hydrochloride—didn't exist until the 1980s, when someone concocted a crystalized form that users can smoke for a more intense high, according to research on the drug. Because it's relatively cheap and can be cooked using reasonably common household chemicals, meth is a popular drug in the U.S. Per a 2016 Journal of Drug Abuse study, it's particularly rampant in the Midwest and rural regions. The Centers for Disease Control and Prevention reports that methamphetamine was one of the 10 substances most often behind drug overdose deaths between 2010 and 2014. The latest National Survey on Drug Use and Health found roughly 900,000 Americans over the age of 12 currently use meth.

Crystal meth can be injected, smoked, snorted, or ingested orally, although the last method means users take a little more time—about 20 minutes, according to a 2008 paper on meth use and its consequences—to feel high. Once they're up, though, they'll stay there for 12 hours. Prolonged use can keep a person awake for days, and regular users require stronger and stronger doses every time.

Related: The Before-and-After Photos Celebrating This Woman’s Sobriety Are Incredible

Watch a hot doctor explain how to treat a headache without drugs:

preview for Ask a Hot Doc: How to Treat a Headache Without Drugs

Fergie—who just released Double Dutchess, her first solo album in 11 years—kicked her habit nearly two decades ago, telling iNews that her hallucinations were ultimately what prompted her to get clean in the first place.

"The drugs thing, it was a hell of a lot of fun… until it wasn’t," Fergie said. "But you know what, I thank the day it happened to me. Because that’s my strength, my faith, my hope for something better."

Related: 'I Was Addicted to Heroin—And It Could Happen To Anyone'

If you or someone you know struggle with drug addiction, Addiction Resource can help you find treatment centers and programs in your area.