Cancer patients often experience mental anguish and stress, but a single dose of a hallucinogen found in psychedelic mushrooms, along with psychological counseling, improved their mindset, two studies said Thursday.

The approach "significantly lessens mental anguish in distressed cancer patients for months at a time," said the findings in the Journal of Psychopharmacology.

The first study, led by researchers at New York University's Langone Medical Center, involved 29 people who were given psilocybin, a naturally occurring component of so-called "magic mushrooms" that is an illegal drug in the United States.

All the people in the study had advanced cancers, whether involving the breasts, gastrointestinal tract or blood.

They had also been diagnosed as suffering from serious psychological distress related to their disease.

After their treatment, 80 percent experienced lasting relief from their distress for more than six months.

A similar study by researchers at Johns Hopkins University involving 51 patients also showed big improvements in anxiety and depression.

Most patients said their quality of life improved, and they had more energy, better relationships with family members and were doing well at work.

"Several also reported variations of spirituality, unusual peacefulness, and increased feelings of altruism," said NYU Langone in a statement.

"Our results represent the strongest evidence to date of a clinical benefit from psilocybin therapy, with the potential to transform care for patients with cancer-related psychological distress," said lead investigator
Stephen Ross, director of substance-abuse services in psychiatry department at NYU Langone.

"If larger clinical trials prove successful, then we could ultimately have available a safe, effective, and inexpensive medication -- dispensed under strict control -- to alleviate the distress that increases suicide rates among cancer patients."

Participants experienced no major side effects such as hospitalization or more serious mental health conditions.

Researchers believe that psilocybin activates parts of the brain that are influenced by serotonin, a chemical thought to play a role in mood and anxiety.

Experts warned that some people should not be considered candidates for psilocybin therapy, including adolescents and those with schizophrenia.