Could you actually have an LSD flashback decades after taking the drug?

Ever hear someone tell a tale about an elderly man who used LSD in his youth going on a fish trip, only to randomly have an LSD-linked flashback and die via drowning? Scary, eh? I remember this urban legend particularly well, thanks to an unusually creepy elementary school assembly about drug awareness.

Stories of flashbacks occurring years after taking LSD are a part of urban legends and internet lore, but do they really happen?

Can the human body store LSD?

The hallucinogenic effect associated with LSD use typically begins thirty minutes after ingestion, and they increase in potency until the four to five mark. After the peak, the effect of the chemical wanes as the hours pass, with psychological effects rarely felt after the eight hour after use passes.

Contrary to urban legend, your body does not store molecules of lysergic acid diethylamide in the base of your spine, subcutaneous fat, or anywhere else in your body. LSD has a short half-life of three to four hours, with the entirety of a dose metabolized by the body within a day and excreted in the urine.

LSD is metabolized quick enough that any trace of the molecule will be eliminated within a day. This leaves none of the molecule available to be stored in the spine or fat, regardless of whether or not spinal fluid or fat provides a stable storage environment for the molecule.

Could you actually have an LSD flashback decades after taking the drug?

HHGP and flashbacks

Here is the good news — if you are going to have an uncomfortable series of adverse effects (like a psychotic episode) from consumption of LSD, the episode will occur shortly after use. Mild flashbacks are also constrained to the days and (possibly) weeks following the last dosage.

A sudden change in perception that occurs in some users months or years after the discontinued use is known as Hallucinogen Persisting Perception Disorder (HPPD). HPPD is linked to persistent LSD use, but is not due to buildup of the molecule within an individual's body.

An individual experiencing such an HPPD flashback undergoes a period characterized by intense visual stimuli — trails following moving objects, a television-like static applied to the field of vision, and color changes. Current medical opinion is divided as to the cause of these flashbacks, with a portion of the medical community labeling it a form of post-traumatic stress disorder while another segments links it to changes in brain morphology tied to the long-term use of LSD or other hallucinogens.

While neither of these schools of thought have enough evidence to provide a definitive origin of HPPD flashbacks that occur late in life, one can rule out their origin from the internal release of LSD due to the molecule's short half-life.

Who started the LSD flashback rumors?

The link between use of LSD during the 1960 and the occurrence of flashbacks after decades of use has an unusual and fallible origin. At a 1991 educational meeting for law enforcement agents held by the Drug Enforcement Agency San Francisco, CA, a speaker allegedly tied the number of homeless in San Francisco to the use of LSD in the 1960s and the Summer of Love.

During the meeting, the speaker suggested that the "re-release" of LSD molecules "hidden" in the bodies of users led to untimely and psychotic flashbacks, thereby increasing the number of homeless, poor, and mentally ill in the city. No official transcript of this meeting exists, although versions of a quote from the speaker exist on the internet.

Regardless of the lack of evidence, making such a statement during an educational meeting for law enforcement could easily cement the link between LSD "hidden" away in one's body leading to modern impairments and form the basis of this urban legend.


Top image from Matt Honan/Flickr. Sources linked within the article.