Impairment and Accidents

Urgent help first

If someone has been injured, is unconscious, or is in danger from their own behavior, call 911 in the US. For a possible poisoning, Poison Help is 1-800-222-1222 (see poisoning: what to do first). This page is education only and gives no guidance on using any substance.

The short answer

Psychedelic and dissociative substances change perception, thinking and judgment. NIDA says their use has been linked to dangerous behavior and injuries, and that people may behave in unusual and sometimes dangerous ways. [1] NIDA also says more research is needed on their effects on driving, operating heavy machinery and other tasks that are dangerous when impaired. [1] Evidence labels used: established (regulator or consistent sources), mixed, insufficient evidence, evidence of harm (documented harm).

Accidents and risky behavior

In the online survey of 1,993 people about their most challenging experience with psilocybin mushrooms, 11% said they put themselves or others at risk of physical harm, 2.6% behaved in a physically aggressive or violent way and 2.7% received medical help. Risk was more likely when the experience was more difficult and when physical comfort and social support were missing. [2] The survey is self-selected and relies on memory, so these are not population rates. Label: evidence of harm (reported), with the true frequency unknown.

Driving: what exists

Classic psychedelics (psilocybin, LSD, mescaline, DMT). Proper evidence not found. A PubMed search for driving, simulator or on-road performance studies with psilocybin or LSD found no on-road driving trial to cite, and none of the sources read gives a safe waiting time. Label: insufficient evidence. Because NIDA says the effects of these drugs on driving need more research, this page does not suggest any interval. [1]

Esketamine (Spravato), an approved medicine. The US label says the drug may impair attention, judgment, thinking, reaction speed and motor skills, and tells patients not to drive or operate machinery until the next day after a restful sleep. Patients must arrange transport home. [3] The label reports that in two placebo-controlled driving studies, driving at 6 and 18 hours after a dose was comparable to placebo, but that two treated subjects stopped the driving test at 8 hours because of drug effects. [3]

Two on-road studies match this picture. In 26 enrolled healthy volunteers (24 completed), a single dose given 8 hours before a 100 km highway test did not change car weaving compared with placebo, while an antidepressant used as a positive control did. [4] In 27 patients with depression, next-morning driving and same-day driving (about 6 hours after dosing, repeated over 3 weeks) also did not differ from placebo, while alcohol did impair driving. [5] These studies applied to the approved nasal spray, in small groups, and do not describe ketamine from other sources or other dissociatives. Label: approved medicine (US FDA, treatment-resistant depression and, with an oral antidepressant, depressive symptoms with acute suicidal thoughts or behavior), with a label instruction not to drive until the next day.

Ketamine. NIDA reports that unsupervised ketamine use may have serious health risks, including respiratory depression. [6] No driving study was read for non-medical ketamine. See ketamine.

Salvia divinorum. A laboratory study of its active compound salvinorin A in four healthy adults described disruption of balance and body signals, such as changes in spatial orientation and pressure on the body. [7] No driving or accident study was found. See Salvia divinorum.

Why impairment does not follow a simple pattern

Experience depends on the substance, the product, the person and the setting. Some products have unpredictable contents: US poison center cases involving psychoactive mushroom edibles, which are unregulated and may have unlisted ingredients, were more likely to need admission when more than one substance was involved. [8] Mixing with alcohol or other sedatives adds risk; see combining psychoactive substances, alcohol and sedatives. NIDA notes that fatal overdoses involving these drugs are typically tied to high amounts or drug combinations. [1]

Safety limits

• No source read supports a "safe to drive" time after any psychedelic. Do not infer one from how a person feels.
• Impaired judgment can raise the chance of falls, injuries and unsafe decisions even when the person is not driving. [1]
• Laws on driving under the influence of drugs differ by place; this page is not legal advice, and no jurisdiction's driving law was read for it. See psychedelic legal status by country.