Survey study of challenging experiences after ingesting psilocybin mushrooms : Acute and enduring positive and negative consequences, Theresa M. Carbonaro et al., 2016

Survey study of challenging experiences after ingesting psilocybin mushrooms : Acute and enduring positive and negative consequences

Theresa M. Carbonaro, Matthew P. Bradstreet, Frederick S. Barrett, Katherine A. MacLean, Robert Jesse, Matthew W. Johnson and Roland R. Griffiths

Journal of Psychopharmacology, 2016, 1 –11

DOI: 10.1177/0269881116662634


Acute and enduring adverse effects of psilocybin have been reported anecdotally, but have not been well characterized. For this study, 1993 individuals (mean age 30 yrs; 78% male) completed an online survey about their single most psychologically difficult or challenging experience (worst “bad trip”) after consuming psilocybin mushrooms. Thirty-nine percent rated it among the top five most challenging experiences of his/her lifetime. Eleven percent put self or others at risk of physical harm; factors increasing the likelihood of risk included estimated dose, duration and difficulty of the experience, and absence of physical comfort and social support. Of the respondents, 2.6% behaved in a physically aggressive or violent manner and 2.7% received medical help. Of those whose experience occurred >1 year before, 7.6% sought treatment for enduring psychological symptoms. Three cases appeared associated with onset of enduring psychotic symptoms and three cases with attempted suicide. Multiple regression analysis showed degree of difficulty was positively associated, and duration was negatively associated, with enduring increases in well-being. Difficulty of experience was positively associated with dose. Despite difficulties, 84% endorsed benefiting from the experience. The incidence of risky behavior or enduring psychological distress is extremely low when psilocybin is given in laboratory studies to screened, prepared, and supported participants.

Keywords : Psilocybin, psychedelic, hallucinogen, bad trip, adverse effects, survey, human



Psilocybin, the principal psychoactive component of the Psilocybe and other genera of mushrooms (Presti and Nichols, 2004), has likely been used for millennia within some cultures for religious or divinatory purposes (Guzmán, 2008; Metzner, 2004; Stamets, 1996; Wasson, 1980). Of the US population aged 12 years or older, 8.7% (22.9 million people) reported lifetime use of psilocybin (NSDUH, 2014). In 2004–2005 (the last year data were available), over half (52%) of those who reported initiating use of a hallucinogen in the past year did so with psilocybin (NSDUH, 2007).

Although psilocybin has very low physiological toxicity and is not associated with compulsive drug seeking, it sometimes produces acute and, more rarely, persisting adverse psychological reactions (Johnson et al., 2008; Tylš et al., 2014). Case reports document adverse effects of psilocybin in non-research settings, including short-term distressing psychological symptoms such as fear (Nordic Council of Ministries, 2009; Riley and Blackman, 2008; van Amsterdam et al., 2011), individuals putting themselves at risk for physical harm (Allen et al., 1991; Schwartz and Smith, 1988; van Amsterdam et al., 2011), seeking medical help (Allen et al., 1991; Nordic Council of Ministries, 2009; Mowry et al., 2014), and enduring negative psychological or psychiatric problems (Allen et al., 1991; Nordic Council of Ministries, 2009; Nielen et al., 2004). However, the perceived risk of psilocybin-related harm was found to be very low when evaluated by drug experts (Nutt et al., 2010; van Amsterdam and van den Brink, 2010) and by experienced drug users (Carhart-Harris and Nutt, 2013), and psilocybin was ranked as moderately beneficial by experienced drug users (Carhart-Harris and Nutt, 2013).

Data-reporting systems from emergency rooms and poison centers also confirm that psilocybin is associated with seeking medical treatment (DAWN, 2013; Mowry et al., 2014). However, the incidence of psilocybin toxicity is extremely low relative to other drugs used non-medically. For instance, in 2011, emergency room mentions of problems with psilocybin alone (83 mentions) were only a very small fraction of mentions for heroin alone (10,309 mentions, 0.81%), cocaine alone (9828, 0.84%), and marijuana alone (9711, 0.85%) (DAWN, 2013).

The present study was undertaken to characterize challenging experiences occasioned by psilocybin and the consequences of such experiences. An internet survey was conducted of a large international sample of individuals who reported having had a difficult or challenging experience with psilocybin. Detailed questions were asked about an individual’s single worst “bad trip.” Questions addressed demographics, the set and setting conditions in which psilocybin was ingested, as well as any negative and positive acute and enduring psychological and emotional consequences of the challenging psilocybin experience.