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Early exposure to dogs might curb schizophrenia risk, Maryland researchers say

Man's best friend indeed.

Photo by Mike Burke on Unsplash
  • There is a growing understanding in the medical community of how important the immune system is for our mental health.
  • Much of the risk for mental illness is due to heritability, but a large portion of that risk is also due to the environment.
  • Since children are often exposed to pet dogs at a young age, it could be that their presence affects developing children's immune systems; new research on over a 1,000 study participants suggests that this may indeed be the case.


Scientists estimate that roughly 80 percent of an individual's risk for schizophrenia is attributable to heredity. Unfortunately, there is virtually nothing that can be done to reduce this risk; it's innate. The remaining 20 percent of risk, however, arises from environmental factors.

There are a few ways that we can reduce this risk. We can, for instance, ensure that mothers experience as little stress as possible during pregnancy and that they get adequate nutrition. We can protect children from abuse and trauma and discourage drug use. Now, new research out of Maryland suggests we can also keep a dog in the house.

The immune system and mental health

Many mental illnesses like schizophrenia have an environmental component. There's a developing understanding in the scientific community that mental illness and the immune system are linked. For example, research has shown that victims of childhood abuse are more susceptible to immune disorders and that chronic inflammation plays a role in diseases like depression.

Since pets are often introduced to young, developing children, studying the effect of their exposure on later mental illness rates is a reasonable avenue of research. Cats and dogs can change our environment and our immune systems by introducing allergens, viruses, and bacteria; by changing the home's microbiome; and — not least of all — by relieving stress and changing our brain chemistry as a result.

The researchers in this study therefore recruited a population of 1,371 men and women of varying ages, ethnicities, places of birth, and parental levels of education (as a means of measuring socioeconomic status). Of these, 396 had schizophrenia, 381 had bipolar disorder, and 594 served as controls. Then, these individuals were asked whether they had a pet dog or cat during their first 12 years of life.

Comparing pet ownership and the rates of the two mental illnesses, the researchers discovered that being exposed to a dog before the age of 13 had a huge effect on whether or not that person would later develop schizophrenia. Dog ownership cut the risk down by a staggering 25 percent.

"The largest apparent protective effect was found for children who had a household pet dog at birth or were first exposed after birth but before age 3," said lead author Robert Yolken in a statement.

"There are several plausible explanations for this possible 'protective' effect from contact with dogs," he added. "Perhaps something in the canine microbiome that gets passed to humans and bolsters the immune system against or subdues a genetic predisposition to schizophrenia."

Unfortunately for cat lovers, there was no similar impact from cat ownership on mental illness rates.

"However," said Yolken, "we did find a slightly increased risk of developing both disorders for those who were first in contact with cats between the ages of 9 and 12. This indicates that the time of exposure may be critical to whether or not it alters the risk."

Aside from this slight increase in risk from cats during this specific age range, neither pet appeared to have any effect on bipolar disease.

A major impact

Dog

Photo by Jamie Street on Unsplash

The reason why this effect might exist wasn't made clear during this study — only that a link between dog ownership and schizophrenia exists. Considering that this protective effect was strongest when the very young (0–3) were exposed to dogs, it could very well be the case that exposure to dogs had some benefit for the children's developing immune systems.

But the study has its limitations, and other, unaccounted for variables could be causing this result. For example, dog ownership is more common in affluent families. Even though the study accounted for socioeconomic status through some indirect metrics (specifically, place of birth and parental level of education), it could still be the case that affluent, at-risk children are protected from the kinds of stressors that could trigger schizophrenia in addition to owning a dog.

However, if further research confirms this finding, it could have a major implications for 25,000 people every year — that's one quarter of the annual schizophrenia diagnoses in the U.S. Whether it's because of their microbiomes or their sunny personalities, man's best friend appears to be doing more for our mental state than we might assume.


Hints of the 4th dimension have been detected by physicists

What would it be like to experience the 4th dimension?

Two different experiments show hints of a 4th spatial dimension. Credit: Zilberberg Group / ETH Zürich
Technology & Innovation

Physicists have understood at least theoretically, that there may be higher dimensions, besides our normal three. The first clue came in 1905 when Einstein developed his theory of special relativity. Of course, by dimensions we’re talking about length, width, and height. Generally speaking, when we talk about a fourth dimension, it’s considered space-time. But here, physicists mean a spatial dimension beyond the normal three, not a parallel universe, as such dimensions are mistaken for in popular sci-fi shows.

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A new hydrogel might be strong enough for knee replacements

Duke University researchers might have solved a half-century old problem.

Lee Jae-Sung of Korea Republic lies on the pitch holding his knee during the 2018 FIFA World Cup Russia group F match between Korea Republic and Germany at Kazan Arena on June 27, 2018 in Kazan, Russia.

Photo by Alexander Hassenstein/Getty Images
Technology & Innovation
  • Duke University researchers created a hydrogel that appears to be as strong and flexible as human cartilage.
  • The blend of three polymers provides enough flexibility and durability to mimic the knee.
  • The next step is to test this hydrogel in sheep; human use can take at least three years.
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Predicting PTSD symptoms becomes possible with a new test

An algorithm may allow doctors to assess PTSD candidates for early intervention after traumatic ER visits.

Image source: camillo jimenez/Unsplash
Technology & Innovation
  • 10-15% of people visiting emergency rooms eventually develop symptoms of long-lasting PTSD.
  • Early treatment is available but there's been no way to tell who needs it.
  • Using clinical data already being collected, machine learning can identify who's at risk.

The psychological scars a traumatic experience can leave behind may have a more profound effect on a person than the original traumatic experience. Long after an acute emergency is resolved, victims of post-traumatic stress disorder (PTSD) continue to suffer its consequences.

In the U.S. some 30 million patients are annually treated in emergency departments (EDs) for a range of traumatic injuries. Add to that urgent admissions to the ED with the onset of COVID-19 symptoms. Health experts predict that some 10 percent to 15 percent of these people will develop long-lasting PTSD within a year of the initial incident. While there are interventions that can help individuals avoid PTSD, there's been no reliable way to identify those most likely to need it.

That may now have changed. A multi-disciplinary team of researchers has developed a method for predicting who is most likely to develop PTSD after a traumatic emergency-room experience. Their study is published in the journal Nature Medicine.

70 data points and machine learning

nurse wrapping patient's arm

Image source: Creators Collective/Unsplash

Study lead author Katharina Schultebraucks of Columbia University's Department Vagelos College of Physicians and Surgeons says:

"For many trauma patients, the ED visit is often their sole contact with the health care system. The time immediately after a traumatic injury is a critical window for identifying people at risk for PTSD and arranging appropriate follow-up treatment. The earlier we can treat those at risk, the better the likely outcomes."

The new PTSD test uses machine learning and 70 clinical data points plus a clinical stress-level assessment to develop a PTSD score for an individual that identifies their risk of acquiring the condition.

Among the 70 data points are stress hormone levels, inflammatory signals, high blood pressure, and an anxiety-level assessment. Says Schultebraucks, "We selected measures that are routinely collected in the ED and logged in the electronic medical record, plus answers to a few short questions about the psychological stress response. The idea was to create a tool that would be universally available and would add little burden to ED personnel."

Researchers used data from adult trauma survivors in Atlanta, Georgia (377 individuals) and New York City (221 individuals) to test their system.

Of this cohort, 90 percent of those predicted to be at high risk developed long-lasting PTSD symptoms within a year of the initial traumatic event — just 5 percent of people who never developed PTSD symptoms had been erroneously identified as being at risk.

On the other side of the coin, 29 percent of individuals were 'false negatives," tagged by the algorithm as not being at risk of PTSD, but then developing symptoms.

Going forward

person leaning their head on another's shoulder

Image source: Külli Kittus/Unsplash

Schultebraucks looks forward to more testing as the researchers continue to refine their algorithm and to instill confidence in the approach among ED clinicians: "Because previous models for predicting PTSD risk have not been validated in independent samples like our model, they haven't been adopted in clinical practice." She expects that, "Testing and validation of our model in larger samples will be necessary for the algorithm to be ready-to-use in the general population."

"Currently only 7% of level-1 trauma centers routinely screen for PTSD," notes Schultebraucks. "We hope that the algorithm will provide ED clinicians with a rapid, automatic readout that they could use for discharge planning and the prevention of PTSD." She envisions the algorithm being implemented in the future as a feature of electronic medical records.

The researchers also plan to test their algorithm at predicting PTSD in people whose traumatic experiences come in the form of health events such as heart attacks and strokes, as opposed to visits to the emergency department.

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