Researchers in the United States say the "spiritual" effects of sacred mushrooms can last for more than a year.
Sacred mushrooms, also known as psychedelic or magic mushrooms, contain psilocybin, a plant alkaloid, which affects parts of the brain which respond to the neurotransmitter serotonin.
Psilocybin mushrooms are non-toxic and non-addictive and when eaten can cause nausea, dizziness and sometimes vomiting.
But the mushrooms are also credited with evoking feelings of bliss, relaxation, and wonder, but anxiety, sadness, curiousness and fear can also be experienced and the greatest danger from their recreational use appears to be that of a "bad trip" which can cause severe emotional and psychological distress.
The mushrooms can also be easily mistaken for extremely toxic wild picked mushrooms.
Sacred mushrooms have been used in some cultures for hundreds of years in religious ceremonies and for healing and now scientists say they may help patients with fatal diseases or addictions.
They say there are safe ways to test psychoactive drugs on willing volunteers, providing guidelines are followed.
The team of scientists from Johns Hopkins University in Baltimore, Maryland, gave psilocybin to 36 healthy, well-educated volunteers with active spiritual lives, for a study carried out in 2006.
At the time when they were asked how it felt, most reported having a "mystical" or "spiritual" experience and rated it positively.
The researchers led by Dr. Roland Griffiths found that more than a year later, most still said the experience increased their sense of well-being or life satisfaction, and Griffiths says that is a remarkable finding.
According to Dr.Griffiths, a professor in the departments of Psychiatry and Behavioral Sciences and Neuroscience, in psychological research such persistently positive reports from a single event in the laboratory are rarely seen.
He says the findings lend credence to claims that the mystical-type experiences some people experience during hallucinogen sessions may help patients suffering from cancer-related anxiety or depression and may have potential for the treatment of drug dependency.
Psilocybin is illegal in many U.S. states and the researchers say the key to its use is supervision.
Dr. Griffiths says while some of the group reported strong fear or anxiety for some of the day-long psilocybin sessions, none reported any lingering harmful effects, and no clinical evidence of harm was observed.