This article originally appeared on Tonic.
Melissa Vitale, a 25-year-old publicist in Brooklyn, was doing high-intensity interval training at the gym when the room started to look funny. “I was nearing a brink of exhaustion but wanted to push through the set,” she recalls. “All of a sudden, the walls started melting and the floor was sliding.” Vitale was having a flashback to an acid trip, and it was not her first. “I knew exactly what was happening and slowly laid down on the floor and stretched until it passed,” she says.
Phillia Downs, a 40-year-old shaman in LA, relives her first and only acid trip from 18 years ago about once a year. “I can see walls or wallpaper moving or see dripping water down a wall, like I saw before, or posters moving,” she says.
A 2011 study of 2,679 regular hallucinogen users in Drug and Alcohol Dependence found that 60.6 percent had experienced hallucinations reminiscent of trips while they were sober. LSD is most commonly known to cause flashbacks, though they can also happen with magic mushrooms, DMT, and occasionally MDMA, says James Giordano, professor of neurology and biochemistry at Georgetown University Medical Center. Common visual distortions experienced during flashbacks include perceiving objects as larger or smaller than they are, seeing lines trailing off objects, and noticing something looming at the edge of your vision.
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While flashbacks are often discussed in warnings about the dangers of drugs, neither Vitale nor Downs found the flashbacks upsetting. “[The original trip] was one of the most amazing heart- and mind-opening experiences of my life,” Downs says. “So the flashbacks, I enjoyed. I was amused and fascinated to be seeing photos or walls move.”
Vitale, however, had one anxiety-provoking flashback while driving. “The little white lines on the road were turning into bunnies, and because I was driving late at night in a wooded area where I needed to watch out for wildlife, it was terrifying,” she tells me.
Flashbacks “can be disturbing and trigger anxiety and panic attacks, especially if the individual has an underlying mental health disorder,” says Sal Raichbach, an addiction psychiatrist at Ambrosia Treatment Center. “Hallucinations can be distracting or uncomfortable depending on the setting. They could also occur in a dangerous situation, like when someone is driving.”
Unpleasant flashbacks like these tend to pass pretty quickly, Giordano says. “While intermittent, acute flashbacks might be initially surprising and startling for some, particularity at first, they tend to be very brief and not terribly intense.”
However, psychedelic flashbacks can be more serious. The previously mentioned study found that 4.2 percent of psychedelic users reported distressing or debilitating flashbacks. But Giordano believes this phenomenon is actually much rarer. Matthew Johnson, professor of psychiatry and behavioral sciences at Johns Hopkins University, agrees, estimating that “one in many thousands of users” have flashbacks that interfere with their lives.
When chronic flashbacks compromise someone’s ability to function, this condition is known as hallucinogen persisting perception disorder (HPPD). “Many users report some brief visual abnormalities occurring after acute hallucinogen effects, but only for a small minority of users are these effects troubling or impairing enough to be considered clinically significant or warrant the diagnosis of HPPD,” Johnson explains. “Many users regard such sub-clinical effects as benign and pleasurable.”
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It’s not known exactly what causes flashbacks or why they can happen so far down the line from the original trip, but Raichbach says they could stem from disruptions to neurons that filter out sensory perceptions. Acid flashbacks in particular could result from the way LSD binds to the neurotransmitter serotonin, Giordano says. The serotonin receptor keeps the LSD molecule in place by folding over it, and sometimes, this pair of molecules hides away inside nerve cells. If they rise back up to the surface, the LSD may have another chance to affect the brain, causing the same perceptual shifts experienced during the original trip.
It’s possible that changes in blood flow (like those that occur during exercise) and brain metabolism can cause LSD-serotonin receptor complexes to resurface, Giordano adds, which could potentially explain Vitale’s experience at the gym. Flashbacks can also be triggered by “stress, anxiety, poor sleep, or thinking about the experience itself,” says Santosh Kesari, neurologist and chair of the department of translational neurosciences and neurotherapeutics at Providence Saint John’s Health Center. People on serotonin reuptake inhibitors (which include certain antidepressants) and those with disorders on the psychotic spectrum may be more prone to flashbacks. In addition, regular users are more likely to get flashbacks than one-time or occasional users, Raichbach tells me.
Tricia Eastman, founder of Psychedelic Journeys, a community that facilitates psychedelics ceremonies, has worked with people who have experienced both pleasant and unpleasant flashbacks from 5-MEO-DMT, a hallucinogenic made from toad venom. These people have reported flashbacks triggered by things like cannabis, acupuncture, and meditation. Those who have negative flashbacks tend to have a history of trauma that they’re working through using the substance, she says.
HPPD has never been reported by subjects in clinical studies involving psychedelics, so Johnson believes it stems from conditions particular to illicit drug use, such as contamination of substances, other drugs used simultaneously, and high doses.
Prescription drugs like anti-seizure medications and Klonopin are sometimes used to treat HPDD. Run-of-the-mill flashbacks, however, don’t usually require such treatment. If you experience a disturbing flashback, Giordano recommends reminding yourself that it will likely soon pass. “Focused breathing and other relaxation techniques can help to restore focus and reduce any anxious feelings during the flashback,” he says.
Many of Eastman’s clients have found relief from distressing flashbacks by working with somatic therapists and psychotherapists specializing in psychedelic integration. She also advises them to treat the flashbacks as opportunities for further personal growth. “Allow the re-activations to occur with a state of open, compassionate awareness,” her integration sheets read. “Your mind, body, and spirit will naturally process the experience in a beneficial way if you simply be with what is.”