The study, led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the “la Caixa” Foundation, and Aarhus University, found that young people diagnosed with ADHD or ASD in Denmark now more closely resemble the broader population than those who received the same diagnoses 10 years earlier.

The findings suggest that the increase in ADHD and ASD diagnoses may partly reflect changes in who is being identified and diagnosed, alongside any possible changes in the underlying likelihood of developing these conditions. The research was published in JAMA Psychiatry.

Tracking changes in ADHD and autism diagnoses

Previous studies have identified several characteristics that occur more often among people diagnosed with ADHD or ASD than among the general population. These include being born prematurely or at a low birth weight, having parents with lower levels of education or lower household income, having a parent with a history of psychiatric disorders, and making greater use of healthcare services before receiving a diagnosis.

Researchers wanted to know whether those patterns had changed as ADHD and ASD diagnoses became more common.

To investigate, the team analyzed information from more than 2.1 million children and adolescents in Denmark. The researchers compared more than 71,000 young people diagnosed with ADHD or ASD between 2012 and 2022 with more than 713,000 individuals who had not received either diagnosis.

Differences narrowed over 10 years

Young people diagnosed with ADHD or ASD were still more likely than their peers to have many of the characteristics previously linked with these conditions. However, the size of those differences steadily declined during the study period.

Low birth weight provides one example. At the beginning of the study period, children born with low birth weight were 54% more likely to later receive an ADHD or ASD diagnosis than children born at a normal weight. By the end of the study, the difference had dropped to 17%.

Researchers found comparable declines in the associations involving premature birth and several measures of socioeconomic disadvantage.

“The key message is not that these risk factors are no longer important,” says Magnus Elias Tarp, PhD student at Aarhus University and first author of the study. “What we found is that people diagnosed in recent years resemble the general population more closely than those who received the same diagnoses a decade ago.”

A different way to understand rising diagnoses

Much of the research surrounding ADHD and ASD has examined why diagnosis rates are increasing or which factors are associated with a greater likelihood of developing these conditions. The new study approaches the trend from another direction by asking whether the population receiving diagnoses has itself changed.

The researchers say several developments could potentially contribute to the shift. Awareness of ADHD and ASD has increased, healthcare and education systems may be identifying cases more effectively, access to diagnostic evaluations may have expanded, and the point at which neurodevelopmental characteristics are considered clinically impairing may have changed.

The study cannot determine how much each of these factors contributed. However, the findings indicate that rising diagnosis rates should not automatically be interpreted as evidence that the underlying occurrence of ADHD or ASD has increased by the same amount.

“Our findings help us better understand why ADHD and autism diagnoses have increased so markedly in recent years,” says Oleguer Plana-Ripoll, researcher at ISGlobal and Aarhus University and senior author of the study. “They do not show that these conditions are being overdiagnosed or that they have become less severe. Rather, they indicate that the population receiving these diagnoses has changed over time, and this needs to be taken into account when interpreting current trends. Further research in other countries would be needed to determine whether these findings can be replicated elsewhere,” he adds.

What the findings could mean

Researchers say the results could affect how scientists interpret changes in the prevalence of ADHD and ASD. They may also be important for planning healthcare, education, and social services for people with these diagnoses.

The findings could also influence how researchers interpret reports of improving outcomes among people with ADHD or ASD. Some apparent improvements may result partly from changes in the characteristics of the population now receiving diagnoses, rather than from an improvement in the prognosis of the conditions themselves.

Neither species has an English common name yet. Both are small, with cone-shaped shells measuring about 6 mm in length, and they live on limestone rocks where they feed on algae and lichens.

They also have several unusual features. Unlike most land snails, their eyes are positioned along the sides of the head rather than at the tips of eye stalks. They also carry a circular disk attached to the tail that can seal the shell opening like a door when the animal retreats inside.

New Species Found in Montenegro’s Mountains

The snails were discovered during expeditions organized by Taxon Expeditions, an initiative that allows members of the public to take part in genuine scientific fieldwork.

Between 2018 and 2025, expeditions in Montenegro were carried out through a partnership involving Taxon Expeditions, the non-profit Taxon Foundation, and local collaborators from the Montenegrin Ecologists Society.

The field teams brought together international researchers, citizen scientists, local students, and conservationists to investigate the biodiversity of Durmitor National Park and Komarnica Canyon.

Researchers encountered the snails at several locations while working in the region’s rugged mountain terrain. However, it was not immediately clear that they represented species unknown to science. That became evident only after the animals were dissected and genetically analysed in the field laboratory.

Named After the Places Where They Were Found

The expedition team chose the names during a vote held at camp.

“Cochlostoma dobrido,” was named after the Dobri Do Plateau, located among the peaks of Durmitor National Park. “Cochlostoma komarnica,” takes its name from the stunning but unprotected Komarnica Canyon, which lies south of Durmitor.

“I was amazed that it is still possible to discover new animal species in Europe,” says musician Janine Buisman from The Netherlands, who participated in one of the expeditions and later became a co-author of the paper.

Biologist Jovana Đokić of the Montenegrin Ecologists Society (MES), another author of the study, says the canyons, mountains, and gorges of this part of the Balkans contain extensive biodiversity that remains poorly explored, with many species potentially still waiting to be documented.

Komarnica Canyon Faces a Hydropower Threat

Đokić says that makes plans affecting Komarnica Canyon especially concerning.

“It is all the more worrying that the Komarnica Canyon is targeted to be flooded by a hydropower dam and reservoir. This will destroy this wild river canyon and all the biodiversity in it, including many species still unknown to science.”

– Jovana Đokić

The proposed development has helped make Komarnica Canyon a major focus of organized biodiversity surveys. Researchers and conservation groups are documenting its wildlife in an effort to build a scientific case for protecting the area.

MES is calling for Komarnica Canyon to become part of the UNESCO World Heritage site of Durmitor and for plans for the hydropower project to be abandoned.

“Hydropower is neither green nor sustainable energy when it destroys a unique ecosystem like this,” says Đokić.

“Ariel is pretty unique in terms of icy moons,” said paper co-author Alex Patthoff, a Planetary Science Institute senior scientist.

A Moon With a Surprisingly Violent Past

Ariel is the brightest of Uranus’ moons and the second closest to the planet. At only 720 miles (1,159 km) across (the distance from PSI in Tucson to Salt Lake City, Utah), it ranks as the fourth-largest moon in the Uranian system.

Despite its relatively small size, Ariel has an unusually complex surface. According to the paper’s first author, Caleb Strom, a recent graduate of the University of North Dakota, ancient features such as impact craters sit alongside much younger terrain. Some smooth regions may even have formed through cryovolcanism, a process in which water, ice, or other volatile materials erupt from an icy world rather than molten rock.

Ariel is also covered in fractures, ridges, and grabens, areas where sections of the crust have dropped below the surrounding terrain. Some of these structures occur on scales larger than those found almost anywhere else in the Solar System.

Reconstructing Ariel’s Hidden Interior

Those enormous surface features are what motivated the new investigation. The researchers wanted to determine what Ariel’s interior and orbit may have looked like in the past to produce the fractures visible today.

One key factor is orbital eccentricity, which describes how much an orbit differs from a perfect circle. Changes in Ariel’s interior structure and orbital eccentricity could both influence the amount of tidal stress acting on its icy crust. As the moon travels around Uranus, gravitational forces repeatedly stretch and squeeze it, potentially placing enough stress on the surface to cause large fractures.

“First, we mapped out the larger structures that we see on the surface, then we used a computer program to model the tidal stresses on the surface, which result from distortion of Ariel from soccer ball-shaped to slight football-shaped and back as it moves closer and farther from Uranus during its orbit,” Patthoff said. “By combining the model with what we see on the surface, we can make inferences about Ariel’s past eccentricity and how thick the ocean might have been.”

A Much More Eccentric Orbit

The researchers found that Ariel may once have had an orbital eccentricity of about 0.04, roughly 40 times greater than its value today.

Although 0.04 still represents an orbit that would look nearly circular, that difference would have greatly amplified the tidal forces acting on Ariel. Its orbit would have been about four times more eccentric than that of Jupiter’s moon Europa, whose icy shell is heavily fractured by the continual gravitational stretching and squeezing it experiences.

Those forces may have played a major role in shaping Ariel’s dramatic landscape.

“In order to create those fractures, you have to have either a really thin ice on a really big ocean, or a higher eccentricity and a smaller ocean,” Patthoff said. “But either way, we need an ocean to be able to create the fractures that we are seeing on Ariel’s surface.”

Uranus May Have Had Twin Ocean Worlds

The Ariel study is the second in a series examining what may once have existed beneath the surfaces of Uranus’ moons. Last year, the same research team reported similar results for Miranda, another icy moon orbiting Uranus.

Together, the findings raise the possibility that more than one moon in the Uranian system may have contained a substantial subsurface ocean.

“We are finding evidence that the Uranus system may harbor twin ocean worlds,” said coauthor, Tom Nordheim of Johns Hopkins University Applied Physics Laboratory and principal investigator of the NASA Solar System Workings grant that funded the Miranda and Ariel studies. “Unfortunately, we’ve only seen the southern hemispheres of Ariel and Miranda. But our results can give us predictions of what a future spacecraft might see on the moons’ unimaged northern hemispheres, such as the location of fractures and ridges there. Ultimately, we just need to go back to the Uranus system and see for ourselves.”

What a Future Uranus Mission Could Reveal

Scientists still do not know exactly when Ariel’s deep ocean may have existed, or how long it lasted. However, the new results offer an important foundation for future studies investigating how subsurface oceans on distant icy worlds form, evolve, and potentially disappear over time.

A future spacecraft mission to Uranus could also test the researchers’ predictions by imaging the unexplored northern hemispheres of Ariel and Miranda and searching for the fractures and ridges expected from their models.

This research was also funded by the North Dakota Space Grant Consortium.

These hypothetical black holes would be extraordinarily small and short-lived. If they could be produced at the LHC, their existence might help physicists address some of the deepest unanswered questions about spacetime and gravity. The search also gave researchers a chance to test a new technique for finding rare and previously unknown particles.

“Had we found evidence, we could have begun to directly study quantum gravity,” said Tamas Vami, a researcher in the Compact Muon Solenoid (CMS) experiment who is conducting his postdoctoral work under the guidance of UCSB physics professor Joe Incandela. “It’s a step toward unifying all of the known fundamental forces, which has been a goal of physicists for more than a century.”

The search did not uncover evidence of quantum black holes. But in particle physics, failing to detect something can still provide important information by ruling out where it could exist.

“It’s not a dead-end,” said Incandela Lab graduate student researcher Danyi Zhang. “The result is an exclusion limit, which is a real, publishable statement: ‘If this thing existed with these properties, we’d have seen it. We didn’t, so we can rule it out here.’ That’s genuine knowledge about how the universe works.”

Why Missing Black Holes Still Matter

One of the major puzzles in fundamental physics involves the enormous difference between the scale of the universe we experience and the Planck scale, the fundamental energy scale associated with quantum gravity.

Some physicists have proposed that new physics or an undiscovered symmetry could explain this difference. Crucially, some of those effects might appear at energy levels the LHC can reach.

Years of experiments have already eliminated many theoretical possibilities, and the continued absence of clear signs of new physics at the LHC has become a major challenge for researchers. But similar situations have happened before. Periods in which existing theories struggled to explain observations have sometimes led to radically new frameworks, including Einstein’s theory of relativity.

For that reason, the researchers say null results are an important part of scientific progress. Each one reduces the number of viable possibilities and helps determine where future experiments should look.

Vami’s and Zhang’s results are published in the journal Progress in High Energy Physics (PHEP).

Could the LHC Create Tiny Black Holes?

The possibility of producing black holes at the LHC emerged roughly two decades ago. Physicists proposed that if enough energy were concentrated into an extremely small region, and if extra spatial dimensions (which are already required in string theory) exist, then quantum black holes might form during the trillions of proton-proton collisions created by the accelerator.

These objects would be nothing like the enormous astrophysical black holes found throughout the universe.

“They wouldn’t stick around very long — if you made one, it would disintegrate immediately,” said UCSB physics theorist Steven Giddings, an expert in the paradoxical implications of combining quantum mechanics with gravity, and one of a few scientists at the time who proposed that under certain conditions these tiny voids in spacetime could exist.

When scientists first discussed the possibility, the idea became widely misunderstood. Public concerns focused on the possibility that the LHC might create stable black holes, even though the quantum black holes being considered by physicists would disappear almost instantly.

“People were more focused on the classical behavior of black holes,” said Giddings, referring to those massive voids in spacetime, areas of extreme gravity that can eat whole stars, grow, merge.

The hypothetical black holes produced at the LHC would instead arise from proton-proton collisions combined with the effects of extra spatial dimensions that have never been observed.

Hidden Dimensions Could Make Gravity Stronger

Creating any black hole requires squeezing a large amount of energy into an extremely small region.

“So what do you need to make a black hole? Well, you have to compress some energy into a really small volume,” Giddings explained.

That “really small volume” might extend through two or more hypothetical spatial dimensions that are too small for humans to detect within our 3 + 1 dimension reality.

Such extra dimensions have been proposed as one possible answer to the hierarchy problem, a longstanding question in physics that asks why gravity is dramatically weaker than the other fundamental forces.

One possibility is that gravity is not intrinsically as weak as it appears. Instead, some of its strength could be “leaking” into these extra dimensions. If that were true, the Planck scale could be much closer to the energy scales physicists can experimentally reach.

“Basically, the gravitational force gets stronger, faster, as you go to shorter distances,” Giddings said.

But stronger gravity alone would not be enough. Scientists would also need to concentrate enormous energy into an exceptionally small volume.

That is where the Large Hadron Collider becomes important.

Colliding Particles at Extreme Energies

The LHC accelerates protons to tremendous energies before smashing them together. These collisions give physicists access to extremely small distance scales.

“At the LHC, we’re colliding particles at extremely high energy, which corresponds to tiny distance scales,” Incandela said. “As with microscopy, higher energies mean smaller wavelengths, allowing one to probe smaller distances.”

Researchers are probing scales as small as 10-20 meters at the LHC, a distance that is to an atom, what an atom is to a human.

“The extra dimensions wouldn’t have to be that small,” Incandela continued, “meaning that the LHC proton-proton collisions could be affected by them.”

If gravity became sufficiently strong at those scales and enough energy were concentrated into a tiny enough region, spacetime could theoretically fold in on itself and produce a quantum black hole.

Safety concerns surrounding this idea were eventually addressed through detailed reports and comparisons with ultra-high-energy cosmic rays. These naturally occurring particles have been striking Earth’s upper atmosphere and other astronomical objects at immense energies without producing dangerous effects.

Those comparisons showed that high energy particle collisions do not pose a black hole threat. Any quantum black holes produced under the proposed models would evaporate essentially immediately.

Even so, their extremely brief existence might leave detectable traces in the particles produced as they decay.

Earlier searches by the ATLAS and CMS experiments failed to find such evidence, but those studies had access to much smaller datasets.

With far more collision data now available, researchers could search at higher energies and increase their chances of seeing an exceptionally rare quantum black hole event if such events occur.

Where Quantum Physics Meets Gravity

The search is ultimately connected to one of the biggest unresolved problems in modern physics.

“We have two big theories that describe nature,” Tamas Vami said. “If you want to describe things that are small, you go to quantum field theory. We have the Standard Model to describe all the particles, and it performs exceptionally well in practice. And when you go to the very, very big you have general relativity that would describe how big and massive objects behave.”

Physicists have spent decades trying to combine these frameworks into a single description of nature.

The difficulty is that quantum physics generally describes extremely small objects, while general relativity becomes most important for very massive ones.

The goal is to somehow merge the two theories into a single, unified theory, Vami said, “and that’s really hard to do because you don’t often have a situation which is really tiny but also extremely heavy.”

Microscopic black holes could provide exactly that combination. They would be small enough for quantum effects to become important while also concentrating enough mass and energy for gravity to matter.

Searching for the Signature of a Black Hole

The researchers analyzed CMS detector data collected between 2016 and 2018 and used two approaches to look for evidence of quantum black holes.

One involved a property called sphericity.

“You form a black hole, and it immediately disintegrates. But it has a very spherical decay signature, lots of things going in all directions.”

Another clue would be an unusually large amount of energy in the particles produced by a collision.

“We know that black holes are very high energy,” Danyi Zhang said. “So we basically just take the energy of these particles that are decay products of whatever was created in the collision and sum them together. And if the sum is large enough, we can say that this is the region where we are likely to find the signal.”

Those unusual event patterns also provided an opportunity to use a new analytical method known as “phase-space distance,” developed by UCSB particle theorist Nathaniel Craig and collaborators.

The method works with a machine learning system called a Support Vector Machine, which helps researchers distinguish possible signal events from the enormous background of conventional high energy particle collisions.

In particle physics, “phase space” is a multidimensional mathematical representation incorporating properties such as space, time, energy and momentum into a description of a particle system.

Machine Learning Joins the Search

“We developed the idea of the phase space between events, which can be combined with SVM to help the search,” Craig said.

The method converts the distances between events into a single measurement called an SVM score. Events with larger scores are more likely to resemble the signal scientists are searching for.

This study marked the first time the phase space distance method had been used in a particle physics data analysis.

“We compared phase space distance with the sphericity variable and our conclusion is that phase space distance outperforms sphericity,” Zhang said.

The approach also differs from some “black box” machine learning systems because it is supervised. Researchers can examine the mathematics that produced the result rather than simply accepting an unexplained output.

New Limits on Quantum Black Holes

The search ultimately found no evidence for quantum black hole production.

Based on the theoretical models examined, the result means quantum black holes are unlikely up to about 12 TeV (Tera-electron volts). It also constrains certain theories involving extra spatial dimensions.

Those restrictions are scientifically valuable because they eliminate parts of the range in which these theoretical models could operate.

String theory, for example, assumes a total of 10 dimensions.

“But these measurements say that, assuming the parameters of the theories we considered, you cannot have more than two,” Vami said.

“Theories don’t predict one exact answer,” Zhang added. “They predict a whole range of places a particle could be hiding. Each search clears out part of that range and says ‘not here,’ and over time the map of where new physics could still be, shrinks.”

That process of elimination has repeatedly played an important role in particle physics. The Higgs boson was discovered in 2012 only after decades of experiments gradually excluded one energy region after another.

By eliminating possibilities, physicists can improve their theories, develop new models and design better experiments and detectors.

The Mystery of Weak Gravity Remains

For now, the hierarchy problem is still unresolved.

Without extra dimensions, Giddings estimates that particle collisions would need to reach roughly a million billion times the energy currently achieved at the LHC to produce even the smallest black holes, which would have masses measured in micrograms.

“Theorists will continue to generate ideas and maybe we will do better in figuring things out without experimental data, but it will be difficult,” Giddings said.

“The best guide is experimental data, and that’s what we’d really like to have,” he said, to study quantum gravity, which he calls “the most profound problem in theoretical physics.”

By testing collisions at some of the highest energies currently available, Vami and Zhang have been able to push the Standard Model toward its limits.

Their results provide new guidance for future searches for quantum black holes as a possible solution to the hierarchy problem. Just as importantly, the work shows that the phase space distance method could be used more broadly to search for unfamiliar particles, unusual interactions and other rare phenomena.

Searching for Another Exotic Phenomenon

The researchers also used the same study to hunt for sphalerons.

Sphalerons are not particles. Instead, they are theoretical unstable configurations of particle fields that, like quantum black holes, would be expected to produce relatively spherical energy patterns.

They could potentially help explain another major mystery: why the universe contains matter.

According to current understanding, the Big Bang should have produced matter and antimatter in equal amounts. Those two forms of matter should then have annihilated one another, leaving behind energy rather than the matter-filled universe we see today.

This mismatch is known as the matter-antimatter asymmetry problem.

Researchers found no evidence of sphaleron processes either. That absence allowed them to place limits on how many particle interactions could potentially involve sphaleron transitions.

A More Powerful LHC Is Coming

Future experiments could push the search considerably further.

“We will be putting constraints on what theories can be true,” said Zhang, who is looking forward to new data obtained in the future at the LHC, which is currently shut down for the installation of an ambitious set of upgrades.

The future High Luminosity Large Hadron Collider (HL-LHC) will provide scientists with far larger datasets and more opportunities to detect extremely rare events.

Those experiments will allow researchers “to study fundamental components of matter in more detail,” including processes that may reveal how the early universe evolved.