Tuesday, May 19, 2026

Silver vine or catnip? When cats can choose, silver vine wins

Cats respond more reliably to silver vine than to catnip, despite catnip’s abundant active compounds

Iwate University, Japan

outline of research — video:
The video clip for explaining the article.
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Credit: Reiko Uenoyama

What plant do cats love most?

In Europe and North America, many people would probably answer “catnip.” In Japan, the answer would more likely be silver vine (matatabi in Japanese). Both plants are famous for triggering the well-known feline response: cats rub their faces and bodies against them, roll on the ground, and sometimes lick or chew the leaves.

Previous work by the same research group showed that these plant-derived compounds can repel mosquitoes, suggesting that the behavior may function as a form of natural pest defense. But what happens when cats encounter catnip and silver vine at the same time in a more natural, free-choice setting? Do they choose silver vine, catnip, or both?

A research team from Iwate University and Nagoya University in Japan has found that domestic cats respond more reliably to silver vine (Actinidia polygama) than to catnip (Nepeta cataria) under free-choice conditions. The finding challenges a simple assumption: that a plant containing more active chemical compounds will necessarily produce a stronger behavioral response.

In outdoor experiments in Morioka, Japan, the researchers placed fresh silver vine branches and leaves near living catnip plants in a garden that free-roaming cats could enter and leave. Over ten presentation nights, six identifiable cats were recorded visiting the site. Five of them showed rubbing and rolling behavior toward silver vine, while none showed the same behavior toward either the growing catnip plant or freshly harvested catnip material. The team then compared plant extracts. When catnip and silver vine extracts were presented in the same outdoor setting, cats again showed a stronger tendency to respond to silver vine-derived stimuli.

To test whether this pattern was limited to a small group of local free-roaming cats, the researchers next studied 22 captive purebred cats housed at two facilities in Japan. The cats represented breeds originating from Europe, the United States, and the Middle East. They were tested in a large indoor environment where they could move freely, rather than in individual cages, allowing them to approach, investigate, or ignore the stimuli on their own. When catnip and silver vine extracts were presented simultaneously, 15 cats responded only to the silver vine extract, three responded only to the catnip extract, one responded to both, and three sniffed the papers but did not rub or roll. Overall, cats were significantly more likely to respond to silver vine extract than to catnip extract.

The result was surprising because chemical analysis showed that the catnip used in the study contained abundant active compounds. In fact, the catnip extract contained substantial amounts of cis-trans nepetalactone, a major active compound known to induce the feline response. The total amount of measured bioactive compounds in catnip was about 170 times higher than that in the silver vine extract used in the study.

Further laboratory tests confirmed that these catnip compounds were indeed biologically active. When cats were tested individually in cages, catnip extract and purified nepetalactone isomers found in catnip, compounds made of the same atoms but arranged in slightly different shapes, could trigger the typical rubbing and rolling response. This means that the weak response to catnip under free-choice conditions cannot be explained simply by the absence of active chemicals.

“At first glance, this was counterintuitive,” says Professor Masao Miyazaki of Iwate University, who led the research project. “One might expect a plant containing more active compounds, and compounds that clearly work in laboratory tests, to trigger a stronger behavioral response under free-choice conditions. But that was not what we observed.”

Why cats responded less reliably to catnip remains unclear. One possibility is that fresh catnip may release too much of these active compounds. In other words, the odor may be too strong when cats encounter the living plant. If the odor is intense and continuously released, cats may detect it but be less likely to proceed to rubbing and rolling.

Interestingly, a similar observation was recorded more than 250 years ago. In The Gardeners Dictionary, published in 1768, Philip Miller wrote that cats were especially fond of catmint, now commonly known as catnip, “when it is withered,” but that they tended not to disturb it when a large quantity grew together. Although this was an anecdotal observation rather than a controlled experiment, it closely resembles the pattern suggested by the present study: the amount and presentation of catnip odor may strongly influence whether cats choose to engage with it.

This idea may also help explain why many commercial catnip products use dried leaves. During drying, some volatile nepetalactone isomers may evaporate, possibly reducing the odor to a level that is more effective for inducing the feline response.

“Catnip can make cats respond in laboratory tests, but that does not mean cats will choose it in a more natural, free-choice setting,” says first author Reiko Uenoyama, an assistant professor at Iwate University. “Our study shows that what cats can respond to and what they actually choose are not always the same.”

The findings suggest that real-world behavior depends not only on the presence of active compounds, but also on how the odor is presented and whether animals voluntarily approach and interact with it.

“This study suggests that silver vine is a particularly reliable stimulus for inducing cats’ self-anointing behavior,” says Professor Miyazaki. “It also reminds us that animal behavior should be studied in settings where animals can make their own choices.”

These insights may help improve enrichment materials for domestic cats and provide a broader framework for understanding how chemical cues influence animal behavior in real-world environments.

Journal

Journal of Chemical Ecology

DOI

10.1007/s10886-026-01717-3

Method of Research

News article

Subject of Research

Animals

Article Title

Free-Roaming and Captive Cats Prefer Silver Vine to Catnip for Self-Anointing

Article Publication Date

12-May-2026

DNA floating in seawater is now enough to let scientists monitor the health of America’s dolphin populations

Scientists shows that simply sampling seawater can reveal health of dolphin populations, in a first for conservation

Frontiers

Dolphin school — image:
Common bottlenose dolphins off Southern California, USA. Photograph by John Durban / Holly Fearnbach using a drone at 200ft, authorized by NMFS Research Permit # 22306
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Credit: John Durban / Holly Fearnbach

DNA is everywhere in the world’s oceans – not only packaged inside cells from skin, scales, mucous, feces, and blood, but also floating freely. Sequencing such ‘environmental DNA’ (eDNA) from open water has long been used as a cost-effective way of gauging the number and identity of species in a region, especially when they are rare and elusive or living at great depths.

But species richness is only the most basic biodiversity measure. Until now, eDNA-based methods could only give limited insight into the variables that are most relevant for conservation: the number of individuals, the evenness of the abundances of co-occurring species, or their within-species genetic diversity. But that may be about to change, shows a new, groundbreaking study in Frontiers in Marine Science.

“Here we show that repeated eDNA sampling can be used to estimate the genetic diversity of dolphins that occur in large schools and have very large populations,” said corresponding author Dr Frederick Archer from the NOAA/NMFS Southwest Fisheries Science Center in La Jolla, California.

“This is important because genetic diversity, its outcome measure, can be used as a measure of population size and how ready a population is to react to changes in its environment.”

Around Santa Catalina Island, located 47 km off Long Beach in California, in October and December 2021, the researchers followed 15 schools of dolphins with small boats. They focused on the most common species locally: long-beaked common dolphins, short-beaked common dolphins, common bottlenose dolphins, and Risso’s dolphins. The project was directed the Marine Mammal Institute of Oregon State University (OSU), with funding from the US Office of Naval Research (ONR).

Whenever they encountered a school, the researchers collected a series of two-liter samples of seawater from the surface within 10 meters from the animals. Back in the laboratory, they sequenced each sample’s mitochondrial eDNA in the laboratory – paying particular attention to quality control – and compared the observed genetic diversity to that in public databases.

The scientists found 836 mitochondrial sequence variants in 126 water samples, of which 76% were from cetaceans and 60% from toothed whales. Overall, 29% were from the species of the school, which had been visually identified. Long-beaked common dolphins had the greatest genetic diversity, followed by short-beaked common dolphins, while Risso's and bottlenose dolphins proved much less diverse around Santa Catalina.

“Our study demonstrates the utility [of eDNA surveys] for efficiently assessing and comparing genetic diversity in social odontocetes,” concluded the authors.

The data indicated that in general, taking as many samples as feasible from multiple schools helps to gain an accurate estimate of the genetic diversity. The researchers calculated that between 60 and 72 liters of seawater would be enough for long-beaked common dolphins, the most diverse around Santa Catalina. But they emphasized that this volume may depend on the species.

“The temperature and salinity of the water are expected to affect the rate of skin shedding. Faster swimming affects shedding as well as respiration, so that DNA will be released through air blows at different rates. Feeding rate and prey should affect the frequency and composition of their defecation. The size of schools and behavior are also likely to be important, as bodies rubbing together or aerial activity such as breaching will promote shedding,” hypothesized Archer.

The authors are eager to put their methods to good use in conservation, now that they have been proven to work.

“It would be good to start eDNA monitoring programs as soon as possible that were not possible before. For example, we will be able to see how species composition in very small areas change over the course of a year – including rarer species that we don’t often detect on visual surveys,” said Archer.

“This can give us a lot of information on habitat use and will also allow us to potentially observe how environmental changes and anthropogenic effects such as pollution or underwater sound affect species distributions.”

Journal

Frontiers in Marine Science

DOI

10.3389/fmars.2026.1756593

Method of Research

Experimental study

Subject of Research

Animals

Article Title

Estimating genetic diversity of abundant oceanic dolphins through repeated environmental (e)DNA sampling

Article Publication Date

19-May-2026

Common bottlenose dolphins off Southern California, USA. Photograph by John Durban / Holly Fearnbach using a drone at 200ft, authorized by NMFS Research Permit # 22306

Long-beaked common dolphins off Southern California, USA. Photograph by John Durban / Holly Fearnbach using a drone at 200ft, authorized by NMFS Research Permit # 19091

Risso's dolphins off Southern California, USA. Photograph by John Durban / Holly Fearnbach using a drone at 200ft, authorized by NMFS Research Permit # 19091

Risso's dolphins off Southern California, USA. Photograph by John Durban / Holly Fearnbach using a drone at 200ft, authorized by NMFS Research Permit # 19091

Risso's dolphins off Southern California, USA. Photograph by John Durban / Holly Fearnbach using a drone at 200ft, authorized by NMFS Research Permit # 19091

Avoidable inequalities remain in cardiovascular disease burden and care

European Society of Cardiology

Key takeaways

The latest cardiovascular disease (CVD) statistics from the ESC Atlas of Cardiology have been published in the European Heart Journal.

CVD continues to be a leading health challenge − the report highlights that CVD is responsible for more than 3 million deaths and 68 million healthy years of life lost annually across ESC member countries.

Great steps forward in cardiovascular medicine are at risk of being offset by the high prevalence of risk factors such as hypertension, dyslipidaemia and obesity. · Middle-income countries continue to experience roughly double the incidence of CVD mortality of high-income nations, underscoring the need for stronger health system investment and more equitable service provision.

Sophia Antipolis, France – 19 May 2026: Cardiovascular disease (CVD) remains one of Europe’s biggest health challenges, according to new data from the European Society of Cardiology (ESC) Atlas of Cardiology, published in the European Heart Journal.1

The ESC Atlas of Cardiology celebrates its 10-year anniversary with the fifth edition of the ESC Atlas report. The publication again demonstrates that CVD is the most common cause of death in more than 50 ESC member countries studied. “The new report shows that CVD was responsible for more than 3 million deaths and 68 million healthy life-years lost annually. These are not abstract statistics − they represent lives lost too early, people living with long-term illness and health systems under growing pressure,” said Professor Adam Timmis, co-first author of the publication.

In line with previous ESC Atlas editions, a central message is the persistent and avoidable inequalities in cardiovascular risk, outcomes and access to care. Middle-income countries continue to experience roughly double the mortality of high-income nations. Professor Steffen Petersen, co-first author, noted: “Europe does not have one cardiovascular reality – ESC Atlas data show that the CVD burden is uneven across ESC countries. While there has been real progress in some countries, in many there are important gaps related to access to advanced diagnostics, procedures and specialist workforce.”

New ESC Atlas data emphasise the growing importance of wider determinants of cardiovascular health, with air pollution levels twice as high in middle-income countries as in high-income countries. In addition, the prevalence of vaping, particularly in young people, underscores the lack of evidence supporting e-cigarettes as an effective smoking cessation tool. The use of e-cigarettes increases the likelihood of later cigarette smoking among minors,2 strengthening the need for clearer regulation and youth-focused prevention policies.

The high prevalence of clinical risk factors such as hypertension, dyslipidaemia, obesity and diabetes remains a concern. Professor Timmis noted: “The progress that has been made in reducing the CVD burden across some ESC member countries is at risk of being offset by the epidemic of obesity and diabetes. The scale of the healthy life-years lost due to modifiable risk factors supports urgent efforts to improve prevention across a person’s life and aid early detection and guideline implementation. The medical and economic costs of inaction are huge.”

Female disadvantage is evident across many of the variables studied, including lower access to key cardiac procedures. While the ESC Atlas report highlighted that 40% of cardiologists are women, only 11.5% of interventional cardiologists are women, with even fewer women in cardiac surgery (8.8%).

“A major strength of the ESC Atlas is the contributions of the ESC National Cardiac Societies, which provide not only a picture of disease burden, but also a practical representation of how cardiovascular care is delivered, to whom and by whom in different countries,” explained Professor Petersen, who concluded: “The ESC Atlas is not just about describing the problem. Mapping these gaps is the first step towards closing them with targeted policy action, guiding investment and supporting national cardiovascular strategies that reduce inequalities.”

In addition to the fifth published edition, interactive data dashboards showing inequalities in CVD across more than 50 countries are freely available at eAtlas.

Previous editions of ESC Atlas data were presented to EU health ministers as part of discussions that led to the recent launch of the Safe Hearts Plan, which aims to anchor CVD at the centre of Europe’s public health agenda.

ENDS

References:

[1] Timmis A, Petersen SE, et al. European Society of Cardiology: Cardiovascular Disease Statistics 2025. Eur Heart J. 2026. https://academic.oup.com/eurheartj/article-lookup/doi/10.1093/eurheartj/ehag345

[2] Hammond D, Reid JL, Cole AG, et al. Electronic cigarette use and smoking initiation among youth: a longitudinal cohort study. CMAJ. 2017;189:E1328−E1336.

Journal

European Heart Journal

DOI

10.1093/eurheartj/ehag345

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

European Society of Cardiology: cardiovascular disease statistics 2025

Article Publication Date

19-May-2026

Loneliness increased over 40 years in Japan

Researchers found a rise in loneliness from 1983 to 2023 using a cross-temporal meta-analysis

Chuo University

image:
Trends in loneliness in Japanese society from 1983 to 2023. The horizontal axis represents the investigation year of study, and the vertical axis represents mean of the UCLA Loneliness Scale scores. Each dot corresponds to an individual data point. As shown by the trend line, loneliness in Japan increased over the 40 years.
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Credit: Momo Homma, Master's Student, Graduate School of Letters, Chuo University Kenkichi Takase, Professor, Department of Psychology, Faculty of Letters, Chuo University

Despite widespread claims that social changes have intensified loneliness, no study has yet examined how loneliness has changed over time in Japan. To address this gap, graduate student Momo Homma from the Department of Psychology at Chuo University, Japan and Professor Kenkichi Takase from the same institution conducted a cross-temporal meta-analysis to investigate how loneliness has changed over time in Japan and identify the factors contributing to this change. The results indicated that loneliness increased in Japan from 1983 to 2023. Furthermore, the increase was particularly pronounced among adolescents and women, and social indicators such as marriage rates were found to covary with loneliness. These findings provide a foundation for future research on loneliness and help identify target populations for interventions aimed at reducing loneliness.

Previous research has linked loneliness to mental and physical health, as well as to health-related behaviors, and has also shown that it is associated with increased mortality risk. The World Health Organization has identified loneliness as “a global public health concern” and has positioned it as a public health priority. In Japan, loneliness is also emerging as a social issue. However, its long-term trends have not been systematically examined. Therefore, in this study, we used a cross-temporal meta-analysis to investigate how loneliness has changed over time in Japan.

In this study, we searched four databases (PubMed, Web of Science, J-STAGE, and CiNii) to identify studies conducted in Japan that used the UCLA Loneliness Scale. In the English-language databases, we used the search terms “UCLA Loneliness Scale, Japan” and “UCLA Loneliness Scale, Japanese.” In the Japanese databases, we searched for “UCLA Loneliness Scale (in Japanese).” We also included additional studies identified through the review process. The search yielded 333 records. After removing duplicates and screening abstracts, 251 studies remained. We then applied the exclusion criteria and conducted a full-text review, resulting in a final sample of 81 studies comprising 183 datasets (N = 49,054) included in the meta-analysis. Subsequently, we performed data coding and score adjustments.

The main analysis revealed a significant increase in UCLA Loneliness Scale scores from 1983 to 2023. This finding suggests that loneliness in Japan may have worsened over the past 40 years. Secondary analyses also revealed effects of developmental stage and gender. Regarding developmental stage, loneliness increased among adolescents. In terms of gender, although men consistently showed higher levels of loneliness, an increasing trend was observed only among women. Further analyses also revealed the influence of social indicators. When loneliness scores were compared before and during the COVID-19 pandemic, loneliness score was higher during the pandemic. In addition, the increase in loneliness covaried with social indicators such as the number of single-person households, marriage rates, GDP, and Internet use.

This study is the first to investigate how loneliness has changed over time in Japan. The results show a substantial increase in loneliness and factors contribute to this trend. The findings highlight loneliness as a pressing social issue and provide key evidence supporting the need for further scientific research and policy interventions.

Increases in loneliness were particularly evident among adolescents and women, highlighting the need for targeted support. To address loneliness in adolescence, future work will explore whether dietary interventions can help reduce loneliness. If effective, we will further examine the underlying biological mechanisms, including the gut–brain axis. To support women, particularly mothers, we are developing a generative AI–based support system (an “AI childcare worker”) designed to alleviate loneliness. We will evaluate its effectiveness and work toward its real-world implementation.

【Glossary】

1) Loneliness
Loneliness is defined as a subjective negative emotional state resulting from a perceived discrepancy between desired and actual interpersonal relationships. It is distinguished from social isolation, which denotes an objective lack of social connections.

2) Cross-temporal meta-analysis
A method of meta-analysis that uses mean scores of psychological measures to examine changes in those measures over time. Meta-analysis integrates findings from multiple studies to draw overall conclusions and is considered a high level of evidence.

Journal

Frontiers in Psychology

DOI

10.3389/fpsyg.2026.1824941

Method of Research

Meta-analysis

Subject of Research

Not applicable

Article Title

Increasing loneliness in Japan, 1983–2023: a cross-temporal meta-analysis

New research finds low-dose buprenorphine may help sustain ketamine’s benefits for suicidal ideation

American Psychiatric Association

San Francisco, California, May 18, 2026 — New research published online today in the American Journal of Psychiatry finds that low-dose buprenorphine, given after a single ketamine infusion, significantly sustained reductions in suicidal ideation in adults with major depressive disorder. The randomized, double-blind, placebo-controlled trial is the first to show that a pharmacologic intervention may help maintain and build on ketamine’s anti-suicidal effects in this at-risk population.

Ketamine is known to reduce suicidal thoughts very quickly, often within hours; however, its benefits usually do not last long. In the study, 50 adults with major depression and clinically significant suicidal ideation received a single open-label intravenous infusion of ketamine. Two days later, participants were randomly assigned to receive either low-dose buprenorphine or a placebo for four weeks. Forty-five participants completed at least one week of follow-on treatment and were included in the primary analysis. Both groups improved, but the buprenorphine group showed significantly greater reductions in suicidal ideation over time than the placebo group. At week four, there was a 76% reduction in suicidal ideation in the ketamine and buprenorphine group, compared to a 43% reduction in the ketamine and placebo group.

Depression scores improved in both groups during the study, but differences between groups were not statistically significant. No serious treatment-related adverse events occurred.

Two of the study’s authors presented their findings at the Annual Meeting of the American Psychiatric Association. The findings are notable because there are currently no FDA-approved medications specifically indicated to reduce suicidal ideation in major depressive disorder. The authors conclude that the ketamine-buprenorphine sequence may represent a potentially scalable and safe therapeutic option for patients at risk of suicide.

"This is the second trial to indicate that buprenorphine at low doses reduces suicidal ideation in major depression,” said Allen Schatzberg, M.D., senior author on the study. “However, unlike earlier reports, the degree of reduction was enhanced markedly by pretreating with intravenous ketamine. The similarities of the buprenorphine findings and the availability of both drugs for clinical use could rapidly increase the potential adoption of the sequence as a treatment strategy to reduce suicidality.”

Christine Yu Moutier, M.D., chief medical officer of the American Foundation for Suicide Prevention (AFSP), which was one of the study's funders, was also at the presentation to underscore the study’s importance.

“The Research Grants program at the American Foundation for Suicide Prevention began in the late 1980s at a time when there had been very little investment in research on suicide risk and prevention,” said Moutier. “Over the years, as AFSP has grown, our priority on funding research has helped to grow a mature field of suicide researchers, like Dr. Alan Schatzberg, who is a leader in the field and who mentors others. We are pleased with the results of his important study, one of the first to show the effectiveness of a pharmacologic intervention in helping maintain and build on ketamine’s anti-suicidal effects in an at-risk population."

The authors noted that the study was relatively small and excluded individuals with substance use disorders, meaning additional research is needed to confirm the findings, determine optimal treatment duration, and better understand longer-term safety and effectiveness. They also note that further study is needed on tapering and follow-up strategies.

The article, “Low-Dose Buprenorphine Following Ketamine Treatment for Suicidal Ideation in Major Depressive Disorder: A Randomized, Double-Blind, Placebo-Controlled Trial,” can be found at the American Journal of Psychiatry.

In addition to a Focus Grant from the AFSP, the study was supported by funding from the Pritzker Foundation, the National Institute on Drug Abuse, and Stanford’s Clinical and Translational Science Award Program.

American Psychiatric Association
The American Psychiatric Association, founded in 1844, is the oldest medical association in the country. The APA is also the largest psychiatric association in the world with more than 40,400 physician members specializing in the diagnosis, treatment, prevention and research of mental illnesses. APA’s vision is to ensure access to quality psychiatric diagnosis and treatment. For more information, please visit www.psychiatry.org.

Journal

American Journal of Psychiatry

DOI

10.1176/appi.ajp.20250840

Method of Research

Randomized controlled/clinical trial

Subject of Research

People

Article Title

Low-Dose Buprenorphine Following Ketamine Treatment for Suicidal Ideation in Major Depressive Disorder: A Randomized, Double-Blind, Placebo-Controlled Trial

Article Publication Date

19-May-2026