Health

Study Links High-Potency Cannabis to Greater Risk of Psychosis and Addiction

Published

1 year ago

August 26, 2025

A sweeping new analysis has found that cannabis products with high levels of the psychoactive compound THC may significantly raise the risk of psychosis, schizophrenia, and addiction, heightening concerns among researchers and health officials as cannabis use rises worldwide.

The study, published in the Annals of Internal Medicine, reviewed 99 research papers conducted between 1977 and 2023, covering more than 220,000 people. It concluded that products containing higher concentrations of delta-9-tetrahydrocannabinol (THC) — the chemical responsible for the “high” associated with cannabis — are strongly linked to serious mental health risks.

In Europe, cannabis remains largely illegal, but the European Union Drugs Agency (EUDA) estimates that 4.3 million people use the drug daily or nearly every day. Consumption spans smoking herbal marijuana, eating edibles such as gummies, and vaping potent concentrates like hash oil, “shatter,” and “dabs.”

The potency of these products has increased sharply in recent years. In 2023, cannabis resin in Europe had an average THC concentration of 23%, compared with 11% for herbal cannabis, according to the EUDA. By comparison, researchers considered products with THC levels above 10% or 5 milligrams per serving to be “high-potency.”

The review found that people using such products faced an elevated risk of psychosis and schizophrenia within hours of consumption. Long-term use was also tied to cannabis use disorder — a form of addiction — as well as respiratory problems and dependency symptoms.

“There’s a real warning in these findings,” said Dr. Jonathan Samet, a co-author of the study and professor of epidemiology at the Colorado School of Public Health. “We really need to be carefully watching what the consequences of these products are.”

Findings for more common mental health conditions, such as anxiety and depression, were mixed. Some evidence suggested high-potency THC could ease symptoms in patients with cancer or neurological disorders, but other studies identified harmful effects. Overall, researchers cautioned that the benefits were limited and often tied to specific medical conditions.

The EUDA has long warned that frequent and heavy cannabis use can exacerbate psychiatric problems, increase dependence, and worsen lung health. The new findings, while not yet definitive, reinforce these concerns and could influence future regulations.

Samet noted that any attempt to regulate THC levels would face challenges, since consumers could simply adjust their dosage. “There’s not a simple solution when it comes to potency,” he said. Still, he argued that greater awareness is essential, especially for those with existing mental health vulnerabilities.

“People who say, ‘Well, I’m using THC, what about it?’ … need to know that there are risks,” Samet added.

Health

Medieval Manuscripts Reveal Thousands-Year History of Deadly Sheep Virus

Published

19 minutes ago

September 5, 2026

Web Reporter

DNA recovered from medieval manuscripts has given scientists new clues about the long history of sheep pox, a highly contagious disease that has threatened livestock for thousands of years.

An international team led by researchers at University College Dublin discovered traces of sheep pox virus in parchment used for some of Europe’s historic manuscripts. The findings suggest that animal diseases may have left genetic records in old documents, providing scientists with another way to study how pathogens developed over time.

During the Middle Ages, parchment was commonly made from the treated skin of sheep, goats and cattle. Researchers extracted DNA from the animal skins used to produce centuries-old manuscripts and identified genetic material linked to the sheep pox virus.

The study involved geneticists, historians, virologists, protein chemists and conservation specialists. Louis L’Hôte, the study’s lead author, said the research showed that parchment could preserve DNA from animal pathogens and provide valuable evidence about infectious diseases in the past.

Among the manuscripts examined was the approximately 1,000-year-old York Gospels, considered one of the finest surviving illuminated manuscripts from the late Anglo-Saxon period. Researchers also examined the Corpus Glossary at Corpus Christi College in Cambridge, an early English dictionary, along with other medieval texts from Britain and continental Europe.

In some manuscripts, several pages contained sheep pox virus DNA. Researchers said this could indicate that animals infected with the disease were used to produce the parchment.

The team compared the genetic material recovered from the manuscripts with older DNA samples obtained from Bronze Age sheep teeth. Their analysis indicated that sheep pox has affected livestock for more than 3,700 years.

Sheep pox spreads quickly among animals and can infect a large proportion of a flock. The disease causes fever and skin lesions and can result in death. Outbreaks can also cause major financial losses through reduced milk production, damage to wool and hides, and restrictions on livestock trade.

There is no evidence that sheep pox infects humans.

The research, published in Science Advances, also provided insight into how the virus changed over time. Scientists found that the sheep pox virus genome remained relatively stable during the past several thousand years.

L’Hôte said the finding contrasts with the evolutionary history of some other pathogens, including smallpox. The stability of the sheep pox genome may indicate that important genetic changes occurred much earlier in the virus’s history and helped it adapt to sheep.

Researchers said the work could encourage scientists to examine other archives and libraries for genetic traces of historic animal diseases. Ancient DNA preserved in manuscripts could offer a new source of information about outbreaks that affected livestock and societies long before modern disease surveillance existed.

Health

North African Dust Set to Worsen Air Quality Across Portugal

Published

22 hours ago

September 4, 2026

Web Reporter

Air quality is expected to deteriorate across much of mainland Portugal over the coming days as dust carried from North Africa moves through the atmosphere, with health authorities warning vulnerable groups to take extra precautions.

Portugal’s Directorate-General of Health (DGS) has issued a warning about the expected decline in air quality, particularly in central and southern parts of the country. The dust is being carried by an air mass originating from the deserts of North Africa and is expected to affect much of mainland Portugal.

The Portuguese Institute for Sea and Atmosphere (IPMA) has also forecast suspended dust on Friday and Saturday.

The DGS said the phenomenon is expected to increase concentrations of naturally occurring inhalable particles, particularly PM10, in the air. Exposure to elevated levels of these particles can affect health, with children, older people and those with existing medical conditions considered more vulnerable.

Health officials are advising people to avoid prolonged physical exertion and reduce outdoor activity while the dust remains in the atmosphere. Residents have also been urged to avoid exposure to tobacco smoke and other sources of irritation.

Children, elderly people and those suffering from chronic respiratory conditions, particularly asthma, are being advised to remain indoors whenever possible. People with cardiovascular disease are also considered at greater risk. The DGS recommends that vulnerable residents keep windows closed where possible during the episode.

People receiving treatment for chronic illnesses have been advised to continue taking their prescribed medication.

The air-quality warning comes as parts of Portugal also face a heightened risk of rural fires amid continuing hot weather.

Eleven municipalities in the districts of Bragança, Guarda, Castelo Branco and Coimbra are under the highest rural fire alert level on Friday, according to IPMA.

The weather agency has also issued yellow heat warnings for several districts, including Bragança, Viseu, Évora, Guarda, Faro, Vila Real, Setúbal, Santarém, Lisbon, Leiria, Beja, Castelo Branco, Coimbra and Portalegre. The warnings remain in place until 7pm on Saturday.

Temperatures are expected to ease slightly from the peak recorded on Thursday, particularly along coastal areas, but conditions will remain warm. Temperatures are forecast to stay above 20C in many areas, including regions south of the Tagus River.

The combination of suspended dust and high temperatures could create additional challenges for people with respiratory and cardiovascular conditions. Authorities are therefore urging vulnerable residents to limit outdoor activity and monitor their health while the dust episode continues.

The DGS has stressed that precautions should remain in place for as long as the poor air-quality conditions persist, particularly for people who are more sensitive to airborne particles.

Health

New Zealand Approves MDMA Treatment for Severe PTSD Under Strict Medical Controls

Published

23 hours ago

September 4, 2026

Web Reporter

New Zealand has authorised two psychiatrists to prescribe pharmaceutical-grade MDMA to patients with severe post-traumatic stress disorder (PTSD), making it only the second country after Australia to permit the drug for clinical treatment.

Wellington psychiatrist Dr Gary Wynn and Auckland psychiatrist Dr Tom Paterson received approval from New Zealand’s medicines regulator, Medsafe, following a regulatory process that lasted more than a year. The approvals allow MDMA to be used in controlled clinical settings as part of treatment for eligible patients.

Deputy Prime Minister David Seymour welcomed the decision, saying PTSD can have a devastating effect on people and remains difficult to treat. Seymour previously supported approval of psilocybin, the active compound in magic mushrooms, for severe depression.

PTSD can develop after people experience or face the threat of traumatic events, including combat, sexual assault and the sudden death of someone close to them. Symptoms can include intrusive memories, anxiety, sleep problems and emotional distress.

Treatment options remain limited in many countries. Two antidepressants are commonly approved for PTSD, but they can take several months to produce an effect and do not work equally well for every patient.

New Zealand’s decision is based partly on results from two international Phase 3 clinical trials conducted by the US-based Multidisciplinary Association for Psychedelic Studies (MAPS) and sponsored by its public benefit corporation, Lykos Therapeutics.

A 2021 trial found that 88% of participants with severe PTSD who received MDMA-assisted therapy experienced clinically significant improvement, while 67% no longer met the diagnostic criteria for PTSD.

A second trial, published in 2023, involved people with moderate-to-severe PTSD. Researchers reported that 71.2% of participants receiving MDMA-assisted therapy no longer met the diagnostic criteria by the end of the study.

The evidence has faced scrutiny in the United States. The US Food and Drug Administration rejected approval of the treatment in 2024, citing concerns about the available evidence for its safety and effectiveness.

US regulators also raised concerns about expectancy bias among participants who had previously used MDMA, which could have affected the reliability of the trial findings.

New Zealand has opted for a tightly controlled approach. The Ministry of Health said MDMA treatment would only be provided alongside psychotherapy in a clinical environment and would not involve take-home doses.

Patients must be at least 18 years old, and treatment must be administered by an authorised psychiatrist as part of a comprehensive care plan.

The approvals mark a significant step for psychedelic-assisted therapy in New Zealand while keeping MDMA use under close medical supervision.