Aftereffects: What Is Reported Afterward

Overview

"Aftereffects" covers what is reported after the main effects wear off: later that day, in the following days (sometimes called the subacute period) and months later. Reports include lasting positive change, tiredness and headache, brief recurring perceptual experiences ("flashbacks"), and, rarely, persistent distressing symptoms. This page describes reports. It is not advice about using any substance, and what happens after a research session in a screened volunteer is not a forecast for anyone else.

Evidence labels used here: established (found repeatedly in controlled research), mixed, insufficient evidence and evidence of harm.

The "afterglow" idea

A review chapter on the subacute period says it is often marked by an "afterglow": elevated mood, better well-being, more emotional openness toward self, others and nature, and sometimes a sense of clarity and meaning. It adds that individual responses vary a lot and not all people have positive aftereffects. Some report mood swings, anxiety, panic attacks, sleep problems, depressive symptoms, feelings of alienation, depersonalization, derealization, persisting perceptual changes, flashbacks, prolonged psychosis, mania or suicidal thoughts. [1] Label: mixed. This is a review of mostly descriptive reports and an abstract-level summary; we did not find a source that gives how often each occurs.

What controlled studies report

• Healthy volunteers followed up. Pooled data from eight placebo-controlled psilocybin studies (110 healthy volunteers) found follow-up questionnaires showed no subsequent drug abuse, persisting perception disorders, prolonged psychosis or other long-term impairment in any of the volunteers. [2] Label: established for screened and supported volunteers.
• Reported meaning and change. In an early double-blind study of 30 volunteers, at 2 months the people rated the psilocybin experience as having substantial personal meaning and spiritual significance and attributed sustained positive changes in attitudes and behavior to it. Community observers rated changes consistent with this. [3] These are self-attributed changes by a selected group.
• Headache. In 18 volunteers, psilocybin caused delayed headaches that were transient and lasted no more than a day. [4]

Survey of challenging experiences

In an online survey of 1,993 people about their worst psilocybin mushroom experience, 84% said they benefited. Of those whose experience was over a year earlier, 7.6% sought treatment for enduring psychological symptoms. The authors report three cases that appeared linked to enduring psychotic symptoms and three to attempted suicide. [5] Because the sample was self-selected and recalled events from the past, these numbers cannot be treated as general rates. Label: evidence of harm exists for serious outcomes, but rates are insufficient evidence.

Flashbacks and persistent symptoms

• Brief recurring experiences. In six controlled studies with 142 healthy subjects, 13 reported recurring drug-like experiences after the effects wore off (up to 9.2% overall). They were mostly mild, visual, lasted seconds to minutes and happened within a week of the last administration. Two people had distressing experiences that faded on their own, one had brief pleasant changes for 7 months, and no one had daily-life impairment or met the criteria for HPPD. [6]
• NIDA. NIDA says hallucinogen persisting perception disorder (HPPD) is rare. Flashbacks are typically mild and brief, while people with HPPD report episodes that last longer and can recur even years later, causing distress. Research so far is limited and relies mainly on self-report. [7]
• A review. A review describes two forms: brief "flashbacks" and a chronic type that waxes and wanes over months or years. Dissociative symptoms were consistently associated with HPPD, and many reported perceptual symptoms were not first experienced while intoxicated and were partly associated with pre-existing psychiatric comorbidity. [8]

For more, see persistent perceptual symptoms (HPPD).

After esketamine sessions

The FDA label says patients should not drive or operate machinery until the next day after a restful sleep. [9] Label: approved medicine (FDA; treatment-resistant depression, and depressive symptoms in major depressive disorder with acute suicidal ideation or behavior).

When to get help

New or worsening anxiety, low mood, thoughts of self-harm, unusual beliefs, sleep loss or lasting perceptual changes after an experience are reasons to speak with a health professional. Do not wait to see if it passes if you feel unsafe. In the US, call 988 for a crisis or 911 for immediate danger. This page does not tell anyone to stop or change medicines; speak with the prescriber. See when to seek urgent help and psychedelic adverse effects and contraindications.