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.


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It looks like a busy hurricane season ahead. Probably.

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  • Before the hurricane season even started in 2020, Arthur and Bertha had already blown through, and Cristobal may be brewing right now.
  • Weather forecasters see signs of a rough season ahead, with just a couple of reasons why maybe not.
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Welcome to Hurricane Season 2020. 2020, of course, scoffs at this calendric event much as it has everything else that's normal — meteorologists have already used up the year's A and B storm names before we even got here. And while early storms don't necessarily mean a bruising season ahead, forecasters expect an active season this year. Maybe storms will blow away the murder hornets and 13-year locusts we had planned.

NOAA expects a busy season

According to NOAA's Climate Prediction Center, an agency of the National Weather Service, there's a 60 percent chance that we're embarking upon a season with more storms than normal. There does, however, remain a 30 percent it'll be normal. Better than usual? Unlikely: Just a 10 percent chance.

Where a normal hurricane season has an average of 12 named storms, 6 of which become hurricanes and 3 of which are major hurricanes, the Climate Prediction Center reckons we're on track for 13 to 29 storms, 6 to 10 of which will become hurricanes, and 3 to 6 of these will be category 3, 4, or 5, packing winds of 111 mph or higher.

What has forecasters concerned are two factors in particular.

This year's El Niño ("Little Boy") looks to be more of a La Niña ("Little Girl"). The two conditions are part of what's called the El Niño-Southern Oscillation (ENSO) cycle, which describes temperature fluctuations between the ocean and atmosphere in the east-central Equatorial Pacific. With an El Niño, waters in the Pacific are unusually warm, whereas a La Niña means unusually cool waters. NOAA says that an El Niño can suppress hurricane formation in the Atlantic, and this year that mitigating effect is unlikely to be present.

Second, current conditions in the Atlantic and Caribbean suggest a fertile hurricane environment:

  • The ocean there is warmer than usual.
  • There's reduced vertical wind shear.
  • Atlantic tropical trade winds are weak.
  • There have been strong West African monsoons this year.

Here's NOAA's video laying out their forecast:

But wait.

ArsTechnica spoke to hurricane scientist Phil Klotzbach, who agrees generally with NOAA, saying, "All in all, signs are certainly pointing towards an active season." Still, he notes a couple of signals that contradict that worrying outlook.

First off, Klotzbach notes that the surest sign of a rough hurricane season is when its earliest storms form in the deep tropics south of 25°N and east of the Lesser Antilles. "When you get storm formations here prior to June 1, it's typically a harbinger of an extremely active season." Fortunately, this year's hurricanes Arthur and Bertha, as well as the maybe-imminent Cristobal, formed outside this region. So there's that.

Second, Klotzbach notes that the correlation between early storm activity and a season's number of storms and intensities, is actually slightly negative. So while statistical connections aren't strongly predictive, there's at least some reason to think these early storms may augur an easy season ahead.

Image source: NOAA

Batten down the hatches early

If 2020's taught us anything, it's how to juggle multiple crises at once, and layering an active hurricane season on top of SARS-CoV-2 — not to mention everything else — poses a special challenge. Warns Treasury Secretary Wilbur Ross, "As Americans focus their attention on a safe and healthy reopening of our country, it remains critically important that we also remember to make the necessary preparations for the upcoming hurricane season." If, as many medical experts expect, we're forced back into quarantine by additional coronavirus waves, the oceanic waves slamming against our shores will best be met by storm preparations put in place in a less last-minute fashion than usual.

Ross adds, "Just as in years past, NOAA experts will stay ahead of developing hurricanes and tropical storms and provide the forecasts and warnings we depend on to stay safe."

Let's hope this, at least, can be counted on in this crazy year.

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