Researchers at the University of Helsinki investigated this question and uncovered a striking finding: people with the same depression diagnosis can have dramatically different patterns of brain activity. In some cases, communication between brain regions was unusually strong, while in others, it was weaker than normal.

Depression is a major global health concern. According to the World Health Organization (WHO, 2025), approximately 332 million (5.2%) adults worldwide are affected. In Finland, depression is the leading individual cause of both extended sick leave and disability pensions.

Brain Study Reveals Five Distinct Depression Profiles

To investigate the biological differences associated with depression, researchers examined brain activity in 263 people diagnosed with major depressive disorder and 75 healthy participants who served as a comparison group.

The analysis revealed five distinct groups based on differences in functional connectivity, a measure of how closely activity in different brain regions is coordinated. When two regions show synchronized activity, it suggests they are working together as part of a larger brain network. However, stronger connectivity does not necessarily mean the brain is functioning better.

“What was particularly interesting was the contrasting patterns of brain activity found under the umbrella of the same depression diagnoses. In some individuals, the functional connectivity between brain regions was stronger than usual, while in others it was weaker,” says Director Satu Palva of the Neuroscience Center, University of Helsinki.

These differences were also associated with particular symptoms. Participants in one group showed especially strong connections between brain regions, along with more pronounced substance abuse problems. Another group displayed weaker connections and a greater prominence of post-traumatic stress disorder (PTSD) symptoms.

The contrasting results could help explain why earlier studies examining the brains of people with depression have sometimes reached conflicting conclusions. If researchers study different combinations of patients, they may observe very different patterns, even though everyone involved has received the same diagnosis.

The findings add to growing evidence that depression may not have a single, consistent biological signature. Instead, the condition could involve several distinct patterns of brain function.

The Five Brain Patterns Linked to Depression

The researchers classified participants with depression into five groups based on how strongly different brain areas communicated and the frequencies at which their activity was coordinated.

Each group had a characteristic pattern of brain connectivity and associated symptoms:

Group 1: Strong connectivity and severe symptoms

Participants generally showed relatively strong connections between brain regions. This profile was associated with more severe symptoms across several areas, including depression, anxiety, rumination, and reduced ability to function in daily life. Rumination refers to repeatedly dwelling on distressing thoughts, worries, or negative experiences.

Group 2: Weaker connectivity and milder depression

This group was characterized by relatively weak communication between brain regions. Compared with the other groups, participants generally experienced milder symptoms.

Group 3: Widespread weak connectivity and trauma symptoms

People in this group showed reduced connectivity across substantial portions of the brain. Symptoms associated with post-traumatic stress disorder (PTSD) were particularly prominent.

Group 4: Mixed connectivity and multiple challenges

This profile combined unusually strong connections in some brain regions with weaker connections in others. Participants tended to experience more severe depression, greater substance abuse problems, and lower overall well-being.

Group 5: The strongest connectivity and substance abuse symptoms

Participants in the fifth group had the strongest connections between brain regions of any group identified in the study. Substance abuse was a particularly prominent issue, while trauma related symptoms were less pronounced than in the other groups.

Importantly, all five groups also showed differences from the healthy participants. These distinctions extended beyond whether brain connections were strong or weak. The groups also differed in which brain regions were involved and the frequencies at which their activity was synchronized.

Together, the patterns suggest that people diagnosed with depression may experience substantially different changes in how their brain networks operate.

Measuring Brain Activity With Millisecond Precision

To capture these differences, the scientists used magnetoencephalography (MEG), a brain imaging technique that detects extremely faint magnetic fields produced by electrical activity in the brain.

Unlike methods that track slower changes associated with brain activity, MEG can follow electrical signals as they unfold over extremely short periods. This makes it particularly useful for investigating the timing and coordination of communication between brain regions.

Using MEG, the researchers recorded brain activity in all 263 participants with depression and the 75 healthy control subjects.

“MEG enabled us to monitor electrical brain activity with millisecond precision, helping us get closer to what actually happens in the brain at any given moment. Previously, depression phenotypes have been studied using methods with slower responses,” Palva notes.

This high level of temporal precision allowed the team to examine rapid changes in brain activity that might be difficult to distinguish using slower measurement techniques.

By studying these fast signals, the researchers were able to identify differences not only in the strength of connectivity but also in the frequencies at which brain regions appeared to work together.

Could Brain Activity Lead to More Personalized Depression Treatments?

The discovery raises an important possibility for the future of mental health care: treatments might eventually be selected partly according to a person’s individual pattern of brain activity.

Today, finding an effective depression treatment can involve trying different medications or therapies and evaluating how well each works. Because patients can respond differently to the same treatment, identifying the most suitable approach is not always straightforward.

Brain activity measurements could eventually provide additional information to help guide these decisions. However, the researchers emphasize that their findings are not yet ready for clinical use.

“We’re not yet at the point where brain measurements can be used to choose the right treatment for patients, but the study does show one possible route,” Palva says.

A major long-term goal is to better understand how particular symptoms relate to the way brain networks function. Connecting these biological patterns with patients’ experiences could help researchers develop more precise ways to identify and characterize depression.

Eventually, such knowledge might allow doctors to determine which therapies are most likely to help individual patients, potentially reducing the amount of trial and error involved in treatment.

For now, the five brain profiles offer a different way to understand depression. Rather than assuming that one diagnosis corresponds to one underlying pattern of brain activity, the findings suggest that depression can involve markedly different biological changes, sometimes even in opposite directions.

The research was carried out in collaboration with Aalto University and Helsinki and Uusimaa Hospital District (HUS).

High-intensity interval training (HIIT), which involves alternating short bursts of demanding exercise with easier recovery periods, may be especially helpful for older adults who want to reduce fat without sacrificing lean muscle.

In a study published in Maturitas, researchers from the University of the Sunshine Coast compared three different exercise intensities. Although participants across the groups experienced modest fat loss, HIIT stood out for its ability to reduce fat while maintaining lean tissue.

“We found that high, medium and low intensity exercises all led to modest fat loss but only HIIT retained lean muscle,” said lead author and exercise physiologist Dr. Grace Rose of the University of the Sunshine Coast.

The results highlight an important distinction in healthy aging: losing weight is not necessarily the same as improving body composition.

Six Months of Exercise Revealed a Key Difference

The Australian research team investigated how workout intensity affects body composition, meaning the proportions of fat, muscle and other tissues that make up the body.

A total of 123 healthy older adults from the Greater Brisbane region participated in the trial. Their average age was 72, and their average body mass index was approximately 26kg/m², which the researchers described as normal for adults over 65.

Participants completed three supervised gym sessions each week for six months. Each session lasted 45 minutes, and participants were assigned to high-intensity intervals, moderate-intensity exercise, or a low-intensity comparison group.

To track changes, researchers measured body composition at the beginning of the study, after three months, and again at six months. They used a specialized scanning technique that estimates fat and lean tissue throughout the body.

The findings revealed that exercise intensity made a difference.

Both high- and moderate-intensity training significantly reduced fat mass, with larger improvements than those seen in the low-intensity group. However, the two more demanding approaches differed in their effects on lean tissue.

“While moderate training reduced fat mass, it also caused a small decline in lean muscle,” Rose said.

Participants performing HIIT, meanwhile, reduced fat without experiencing the same decline in lean mass.

This could be particularly valuable later in life, when maintaining muscle becomes increasingly important for physical independence. Strong muscles help people climb stairs, get out of chairs, maintain balance, and carry out everyday activities.

One important distinction is that the scans measured lean tissue rather than muscle strength directly. Lean mass includes muscle but also other tissues and water, so changes in these measurements do not necessarily translate into equivalent changes in strength.

High-Intensity Exercise Also Reduced Abdominal Fat

The researchers found another potentially important benefit involving fat stored around the middle of the body.

“Both high and moderate intensities improved the composition of weight carried around the middle. Further analysis is needed of the low intensity results.”

The original study found improvements in visceral adipose tissue among both the high and moderate intensity groups.

Visceral fat is different from the fat that sits directly beneath the skin. It accumulates deeper in the abdomen, surrounding internal organs such as the liver and intestines.

Excessive amounts of this fat have been linked to insulin resistance, cardiovascular disease, and other metabolic problems.

According to Rose, these findings matter because body composition can influence the development and progression of chronic diseases as people age.

While body weight and body mass index provide useful general information, they do not reveal how much fat or muscle a person carries, or where that fat is stored.

Someone who loses fat while maintaining muscle may experience a more favorable change in body composition than someone who loses a similar amount of weight along with valuable lean tissue.

Still, the original researchers emphasized that the improvements were relatively small. They cautioned that the differences were not clearly clinically meaningful when compared with lower intensity exercise, particularly after accounting for measurement uncertainty.

Why HIIT May Help Aging Muscles Stay Strong

One possible explanation for HIIT’s advantage lies in the way it challenges the body.

Rather than exercising at the same pace throughout a workout, HIIT repeatedly pushes the cardiovascular system and working muscles through periods of intense effort, followed by easier activity.

University of the Sunshine Coast Associate Professor of Physiology and study co-author Mia Schaumberg explained how the training worked.

“High-intensity training in this study involved repeated short bursts, or intervals, of very hard exercise — where breathing is heavy and conversation is difficult — alternated with easier recovery periods.

“HIIT likely works better because it puts more stress on the muscles, giving the body a stronger signal to keep muscle tissue rather than lose it.”

This explanation is consistent with the idea that muscles adapt to the demands placed on them. When exercise provides a sufficiently challenging stimulus, the body has more reason to maintain the tissues needed to perform that activity.

Muscle preservation is especially important because aging is often accompanied by a gradual decline in muscle mass and strength. In more advanced cases, this can contribute to sarcopenia, a condition characterized by reduced muscle strength and quantity that can interfere with mobility and independence.

Schaumberg said the original research could help people make more informed decisions about exercise and healthy aging.

When the university publicized the findings in early 2026, she also highlighted their relevance to people setting fitness goals.

“With the festive season now behind most of us and New Year’s resolutions in full swing, this research can help inform people’s plans for healthy aging in 2026,” she said.

The research involved collaborators from UniSC’s Healthy Ageing Research Cluster and The University of Queensland.

More Recent Studies Reveal Additional Benefits of HIIT

Research published in 2026 has provided further insight into how HIIT affects older adults, although it also suggests that intense workouts are not necessarily superior in every situation.

One 2026 study, published in Medicine & Science in Sports & Exercise, investigated whether older adults could benefit from completing HIIT at home with remote supervision.

The study involved 20 adults aged 61 to 74 who exercised using a specialized machine that let them work their arms and legs without bearing their body weight.

After eight weeks of training, participants had lost an average of approximately 1.4 kilograms, or about 3 pounds, of fat mass. Their aerobic fitness also improved substantially.

Participants completed 96 percent of their scheduled workouts, and the researchers reported no exercise-related adverse events.

Although the trial was small, its findings suggest that appropriately supervised HIIT programs may offer benefits outside a conventional gym.

Another 2026 randomized trial, published in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences, compared HIIT with continuous moderate-intensity exercise in older adults living with HIV.

In that study, participants completed 16 weeks of exercise, with both groups also performing resistance training.

Unlike the original Australian study, both exercise groups experienced reductions in fat and increases in lean mass. The researchers found no statistically significant difference between the two groups in those body composition changes.

These results suggest that workout intensity is not the only factor that matters. Resistance training, which challenges muscles through weights or other forms of resistance, may also help preserve or increase lean tissue.

The populations and training programs differed, so the findings should not be treated as a direct contradiction of the Australian results.

Is HIIT Really the Best Exercise for Older Adults?

A broader scientific review published in the Journal of Clinical Medicine in August 2026 offers additional perspective.

Researchers examined 25 reports involving approximately 2,818 participants to assess how HIIT and other forms of interval training affect older adults.

The most consistent benefits involved cardiovascular fitness, including improvements in the body’s ability to use oxygen during exercise.

Some studies also reported improvements in physical function and metabolic health. However, the review did not establish that HIIT was consistently better than moderate-intensity exercise.

The researchers noted that differences between exercise programs, participant characteristics, and study methods made it difficult to identify a single optimal training approach.

Taken together, the findings suggest that HIIT can be a useful tool for healthy aging, but it is not the only way to improve fitness or protect muscle.

For adults over 65, the Centers for Disease Control and Prevention recommends a combination of aerobic exercise, muscle strengthening activities, and exercises that improve balance.

Higher intensity workouts may be appropriate for some older adults, but people who are inactive or have medical conditions may benefit from gradually building up their fitness and seeking guidance before beginning a demanding program.

The central message from the Australian study remains compelling: what happens to muscle during fat loss may be just as important as the amount of weight someone loses.

HIIT showed promise because it helped participants reduce body fat while maintaining lean tissue. Combined with newer findings, the research reinforces the value of exercise programs that support not just a lower number on the scale, but also the strength, fitness, and physical function needed for healthy aging.

The four astronauts spent 237 days in orbit, traveled more than 100 million miles, and completed thousands of trips around Earth while carrying out scientific experiments that could help shape future missions to the Moon and Mars.

NASA will host a news conference at 3:30 p.m. EDT on Thursday, Oct. 15, at Johnson Space Center in Houston, where returning crew members will discuss their experiences and research accomplishments.

“Jessica, Jack, Sophie, and Andrey spent 237 days living and working in orbit, traveled more than 100 million miles, advanced important science, and returned safely home because of the extraordinary expertise and competence of thousands across NASA, SpaceX, and our international partners,” said NASA Administrator Jared Isaacman. “Building the capability, experience, and confidence to do this repeatedly is exactly what will allow us to go farther, and I am grateful to Crew-12 and their families for their service to humanity’s greatest adventure.”

NASA Astronauts Return After 237 Days and 100 Million Miles

The returning crew included NASA astronauts Jessica Meir and Jack Hathaway, ESA (European Space Agency) astronaut Sophie Adenot, and Roscosmos cosmonaut Andrey Fedyaev.

Their spacecraft touched down in the Pacific at 8:34 a.m. PDT. SpaceX recovery teams aboard specialized vessels reached the capsule shortly afterward and brought the astronauts and spacecraft aboard.

Following routine medical evaluations, the crew members will be transported to shore before traveling to NASA’s Johnson Space Center in Houston.

“NASA’s activities supporting the International Space Station — transporting crew, conducting impactful research, and maintaining critical national assets — enable the science, engineering, and risk‑reduction needed for future missions across the solar system,” said Dana Weigel, manager of NASA’s Low Earth Orbit Program at the agency’s Johnson Space Center. “We’re grateful for the dedication across the human spaceflight team that makes this possible, and we’re thrilled to welcome Jessica, Jack, Sophie, and Andrey home.”

Over the course of their 237-day stay, the astronauts circled Earth more than 3,792 times, accumulating over 100 million miles of travel.

For Meir and Fedyaev, Crew-12 marked their second journey into space. Hathaway and Adenot, meanwhile, completed their first space missions.

The crew launched on Feb. 13 at 5:15 a.m. EST, reaching and docking with the International Space Station the following day.

Space Station Experiments Could Help Future Moon and Mars Missions

Beyond the remarkable distance traveled, Crew-12 devoted hundreds of hours to scientific investigations designed to support future human exploration and improve life on Earth.

One research project explored ways to produce stem cells in space for potential use in cell-based medical treatments. Another demonstrated technology capable of producing IV fluids on demand, an ability that could become especially valuable during long-duration missions far from Earth.

The astronauts also investigated how pneumonia-causing bacteria may contribute to lasting heart damage. Understanding this relationship could offer new insights into cardiovascular health.

Other experiments focused on nutrition in space and how individual physical characteristics may influence blood flow during spaceflight. These studies could help researchers better understand the health risks astronauts face during extended stays in microgravity.

Together, the investigations provide valuable information about keeping humans healthy beyond Earth while testing technologies that may eventually support crewed expeditions to the Moon and Mars.

Historic Spacewalks Mark Crew-12 Mission

The mission also included significant milestones outside the space station.

Meir carried out four spacewalks during Crew-12, raising her career total to seven. That achievement places her third among NASA women for the most career spacewalks, behind former astronauts Peggy Whitson and Suni Williams.

Adenot also reached a historic milestone by completing three spacewalks. In doing so, she became the first French woman to venture outside the International Space Station.

With Crew-12 safely back on Earth, NASA has completed another extended mission that combined scientific research, international cooperation, and human spaceflight experience. The knowledge gained will contribute to preparations for more ambitious journeys beyond Earth’s orbit.

NASA has highlighted four events worth watching this month, ranging from Jupiter briefly vanishing behind the Moon to shooting stars created by debris from Halley’s Comet. With crisp autumn evenings and a little luck, skywatchers can enjoy several of these displays without any special equipment.

Jupiter Disappears Behind the Moon on October 6

Before sunrise on Tuesday, October 6, skywatchers in parts of North America had an opportunity to witness an unusual celestial disappearing act. Jupiter, the largest planet in our solar system, slipped behind the Moon’s slender crescent and remained hidden for approximately an hour before coming back into view.

Astronomers call this phenomenon a lunar occultation. It happens when the Moon moves directly between Earth and a more distant object, temporarily blocking our view. Despite its mysterious-sounding name, occultation simply refers to one celestial object concealing another.

The event was visible to the naked eye, although binoculars offered a more detailed look. Observers using optical equipment could also potentially watch some of Jupiter’s moons disappear behind the lunar edge and emerge again.

Viewing opportunities depended on location, with the occultation visible across parts of eastern and central North America. The timing varied geographically, with the event occurring during the early morning hours, around 4 a.m. EDT in some locations.

Draconid Meteor Shower Peaks October 8 and 9

The next celestial attraction comes on the evening of Thursday, October 8, when the Draconid meteor shower reaches its peak. Favorable viewing beginning around 9 p.m. EDT, and the display continues into the early hours of Friday, October 9.

Unlike many meteor showers that are best observed after midnight, the Draconids offer a convenient opportunity to see shooting stars soon after nightfall. That makes them particularly appealing to casual observers who would rather not stay awake until dawn.

Conditions are especially promising this year because the Moon is approaching its new phase. With little moonlight to brighten the sky, even relatively faint meteors should be easier to detect.

The shower gets its name from Draco, a constellation representing a dragon. Although the name might sound like something from a Halloween horror story involving a certain famous vampire, it actually refers to the constellation from which the meteors appear to originate.

The Draconids are generally a modest display, typically producing only a handful of visible meteors each hour. For the best chance of spotting them, head somewhere away from bright city lights, allow your eyes to adjust to the darkness, and scan the open sky for brief streaks of light.

Orionid Meteor Shower Brings Debris From Halley’s Comet

Another opportunity to catch shooting stars arrives on October 21, when the Orionid meteor shower reaches its annual peak.

These meteors have a particularly fascinating origin. They are tiny fragments of material left behind by Halley’s Comet during its journeys through the solar system. When Earth travels through this trail of ancient comet debris, the particles enter our atmosphere at tremendous speeds, creating bright streaks of light as they burn up.

For observers in suburban areas with some artificial lighting, NASA estimates that approximately 3 to 6 meteors may be visible each hour. People watching from darker locations could see somewhat more.

The Orionids take their name from Orion, the famous hunter constellation, because their meteors appear to radiate from that region of the sky. Orion is also home to Betelgeuse, an enormous red supergiant star recognizable by its reddish appearance (but don’t say that name three times in a row!).

There is one potential obstacle to this year’s display. The Moon will be in its waxing gibbous phase, meaning more than half of its visible surface will be illuminated. Its brightness could make some of the dimmer meteors difficult to spot.

Fortunately, viewing conditions should improve after the Moon sets at approximately 3 a.m. local time. By then, Orion will also be higher in the sky, creating a better opportunity to catch meteors during the hours before sunrise.

October’s Hunter’s Moon Lights Up the Halloween Sky

October’s final major celestial highlight is the Hunter’s Moon, which reaches its full phase on October 26 in Universal Time. For observers in much of North America, the Moon will appear full on the evening of Sunday, October 25.

The name Hunter’s Moon comes from traditions associated with the changing autumn season. As crops were harvested, fields became more open, and daylight hours shortened, hunters could take advantage of the bright moonlight to locate and follow animals after sunset.

The Moon will remain a prominent feature of the night sky in the days following its full phase. As Halloween approaches, it will gradually transition into a waning gibbous Moon, with its illuminated portion slowly decreasing each night.

Its lingering glow will provide a fitting backdrop for the final evenings of October, bringing NASA’s month of celestial tricks and treats to a memorable close.