For a person in the middle of a serious drug trip, hallucinations, confusion and raging emotions can make it feel as if he or she is teetering on the edge of insanity.
Depending on the drug and the person, it very well might be true.
In an issue of Marie Claire, singer Stacey "Fergie" Ferguson of the Black Eyed Peas describes a harrowing drug trip from crystal meth -- a drug known for its distressing psychological aftermath.
"I had about 20 different conspiracy theories. I painted the windows in my apartment black so they couldn't see in," Fergie told Marie Claire, explaining that she thought the FBI was after her during her brief addiction to methamphetamines around 2001.
"One day, when I was about 90 pounds, a guy comes up to me. ... I'm searching in the bushes for clues about whatever they're after me for. I'm in a cowboy hat and red lips. He hands me a muffin. I'm thinking, he's in on it," Fergie said.
But for all of the horror in Fergie's FBI scare, she might have been at risk for something worse.
The paranoid delusions of a drug user and the experience of a person with mental health issues barely differ.
"They're the same thing," said Dr. William Compton, director of the division of epidemiology services and prevention research at the National Institute on Drug Abuse.
And unlike other drugs, methamphetamines can directly cause a permanent psychosis -- the technical term for a delusion or a hallucination.
A Cause, or Just a Trigger?
More commonly referred to as a "bad trip," the psychotic symptoms from drugs can arise for a number of reasons.
Marijuana, ecstasy and alcohol withdrawal can all indirectly trigger symptoms of a psychosis. But for these drugs, a secondary culprit also contributes to the hallucinations or delusions, and the mechanism isn't always clear, says Dr. Karen Miotto, director of the University of California-Los Angeles' Alcoholism and Addiction Medicine Service.
"Is it a sleep deprivation? Is it an underlying anxiety disorder that's being exacerbated?" Miotto said.
With methamphetamine and cocaine, it's more the drug, not the person that contributes to the psychotic symptoms.
Cocaine addicts often fall victim to paranoid delusions surrounding the drug -- where is the cocaine? who hid the cocaine? who stole it? -- but methamphetamine addiction is worse, Miotto says.
"With methamphetamine, they're just plan bizarre," Miotto said. "[Methamphetamine users] can think people are after them -- that their child is trying to poison them."
They can go through "a prolonged or persistent psychotic reaction that doesn't end with the 12 hours in the emergency room," Miotto said. Moreover, even if methamphetamines don't cause a permanent psychosis, drug users risk developing depression.
Changing the Brain
Former methamphetamine addict Buffie Cross, 39, started using drugs when she was 26.
"The feeling would start with a rush -- it was euphoric," Cross said. But after only a week she remembers feeling a range of psychological symptoms.
"There were some stuffed animals sitting on the floor, and those things got up and started dancing," she said. "You think you're being followed, or they come out from behind the trees and stuff."
"I became where I obsessively wrote random crap," said Cross, who remembers her writing obsession lasted for two weeks at a time.
Alongside hallucinations and delusions, Miotto says methamphetamine can induce traits similar to obsessive-compulsiveness called "tweaking" on the streets.
In Cross it appeared as writing, in others it shows up as the need to constantly pick things apart and try to put them back together -- usually unsuccessfully.
"If you ask police, they'll tell you 'we can tell it's a meth house because the washing machine is taken apart in the front yard,'" Miotto said.
Even if a methamphetamine user gets treatment for his or her addiction and recovers without a permanent psychosis, depression may soon follow.
Stimulants like methamphetamine deplete dopamine, which is the primary chemical in the "reward pathway" of the brain, Miotto says.
"There is also a theory that drug abuse "resets" the reward pathway, making it more difficult to experience reward or well-being from normally pleasurable experience, Miotto says.
Unfortunately, Cross did not escape this part of methamphetamine addiction.
"I'm not the same person, I can tell you that," said Cross, whose biggest regret was the time drugs took away from her five young children.
"I was a fun-loving person," she said. "I suffer now more from depression."
All Highs Come With a Risk
Meth users make up only 0.3 percent of the U.S. population, according to the 2006 National Survey on Drug Use and Health.
But the 8 percent of people who use other drugs aren't necessarily free from permanent mental health affects.
In the summer, a study in the journal Lancet found that marijuana can increase an individual's risk of developing a psychosis by 40 percent, and possibly up to 200 percent, depending on how long and how much a person used.
The greater a person's risk to develop a psychosis like schizophrenia, the more dangerous it is to use marijuana.
Marijuana may also exacerbate an underlying mood disorder like anxiety, depression or bipolar disorder.
"Those are often the chicken-and-the-egg questions: If people who have depression or anxiety -- symptoms of a mood disorder -- are more likely to use marijuana in the first place," Miotto said.
No Safe Place
For Jim Morrison, 55, the question of the chicken or the egg may never be answered. He started using marijuana at 16 and was diagnosed with bipolar disorder at age 40.
Morrison, the webmaster of the addiction support Web site, mysobrietyspace.com, has been sober for 28 years. But for the better part of a decade, his drug use came with emotional mood swings and occasional paranoia.
"Once I quit drinking or getting stoned, the manic depression episodes got much better,"Morrison said.
At one point in 1979, Morrison became so paranoid about his drug use that he was convinced the Newport Beach, Calif., SWAT team was waiting at his apartment to bust him for an ounce of marijuana.
He parked his cars two blocks from his apartment, hid his stash in an Los Angeles Times newspaper and laid still in the dark for the rest of the night.
"I was thinking, 'oh wow, I beat them,'" he said. The next morning, he realized he'd thrown away his stash along with the newspaper.
"I went flying down the stairs in my underwear and jumped into the Dumpster and found it," Morrison said. When a neighbor caught him in the Dumpster, he realized the marijuana was causing too much trouble. "That's the precipice of insanity."
Cross, who is a frequent user of Morrison's Web site, agrees. She's currently worried about a friend at risk for schizophrenia who's also using methamphetamines.
"It's the luck of the draw and are you willing to gamble? Because it does mess up your mind and some people don't snap out of it," she said.