Note: The Pregistry website includes expert reports on more than 2000 medications, 300 diseases, and 150 common exposures during pregnancy and lactation. For the topic Psilocybin, go here. These expert reports are free of charge and can be saved and shared.
Psilocybin is a chemical agent present in mushrooms of the species Psilocybe semilanceata and Psilocybe cyanescens. Both of these species are known informally as “magic mushrooms,” because psilocybin has hallucinogenic effects. This meanings that the psilocybin alters signals between neurons in the brain to the point of causing hallucinations, apparent perceptions of sensations that do not exist, or perceptions that are extremely altered from what the actual sensation should produce. Psilocybin is part of a category of agents known as psychedelic drugs, which also includes the hallucinogen lysergic acid diethylamide (LSD). The latter was the subject of studies in the middle of the 20th century looking into its potential to treat certain psychiatric conditions. Since that time, a tiny number of small studies have suggested that psilocybin may have some beneficial effects against a type of severe headache called a cluster headache, but mostly the drug is used illicitly for its hallucinogenic effects. Psilocybin usually is taken orally, but it also can be taken intravenously. Psilocybin does not produce what doctors call drug-seeking behavior. This means that it does not cause cravings, nor does it lead people to commit desperate acts, such as crimes, to acquire more of the drug. Consequently, psilocybin is not considered a typical drug of abuse.
But lack of the potential for abuse does not make psilocybin safe during pregnancy. Based on what is understood about psilocybin’s mechanism of action (how it produces its effects), there is no reason to think that magic mushrooms should interfere with your ability to get pregnant, nor on the fertility of your male partner. Also based on what is understood about psilocybin’s mechanism of action, there is little reason to suspect that it would cause a spontaneous abortion (miscarriage) –unless you are in an environment in which the hallucinations resulting from using the drug cause you to become extremely agitated or frightened. However, since data are extremely limited regarding the effects of psilocybin on pregnancy health, or on the developing fetal brain, it is recommended that pregnant women avoid psilocybin and other hallucinogenic drugs, completely.
It’s also noteworthy that certain other hallucinogenic drugs, such as ergotamine and ergometrine, which are related chemically to LSD, can indeed cause a spontaneous abortion, as they are potent simulators of uterine contraction. As for the question of birth defects, there is a lack of human studies investigating this issue, while studies on laboratory animals have not suggested that psilocybin causes birth defects. However, since the drug’s main effect involves chemical signaling in the brain, researchers are not yet sure that maternal use of psilocybin would not lead to any undesirable effect on the fetal brain.
There is no rationale for thinking that psilocybin is any safer on one particular phase of pregnancy, versus another. Very little is known about the effects of maternal psilocybin used in particular patterns, such as binging verses very small doses that are spread out over time. Generally, hallucinogens are not used as binge drugs anyway, such as you might find with alcohol. Typically, hallucinogens are used by people who want to experiment with altered states of consciousness. This includes use of the drugs by some people as part of religious ceremonies.
Psilocybin works by affecting how brain cells interact with a brain chemical called 5HT, or serotonin. These interactions can result in a kind of tolerance in the sense that more psilocybin is needed to produce the same effect that a lower dose produced in the past. Despite this, psilocybin is not thought to produce dependence or withdrawal symptoms in newborns whose mothers used psilocybin during pregnancy.
Use of psilocybin by mothers who are breastfeeding is not recommended. If you really have the urge to use psilocybin after giving birth, you should consider giving your baby one of the many excellent infant formulas that are on the market. On the other hand, the United States is in the midst of a shortage of infant formula, so this option may not be on the table.
The issue of paternal use of psilocybin in connection with fetal and newborn health has not been studied, but based on how psilocybin exerts its effects, there is no rationale for suspecting that paternal use of psilocybin can harm the baby.
In short, there are very few data to be able to determine whether psilocybin use by mothers can harm their babies. Consequently, to be safe, you should avoid this drug while pregnant.