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Immigrants have fewer mental disorders than U.S.-born Americans. Why?
Immigrants who come to the U.S. are significantly less likely than U.S.-born individuals to have mental health problems, according to a new study published in Psychiatry Research.
Immigrants who come to the U.S. are significantly less likely than U.S.-born individuals to have mental health problems, according to a new study published in Psychiatry Research. Using the National Epidemiological Survey on Alcohol and Related Conditions and face-to-face interviews, the study surveyed over 36,000 immigrants and revealed the counterintuitive finding that immigrants are less likely to experience anxiety, bipolar, depressive, and trauma-related disorders.
One would think that the stress of moving to a new country, setting up a new life, and learning a new culture would be an assault on an immigrant's mental health. There's no doubt that doing so is stressful, but it turns out that the very reasons why immigration is so difficult are the same reasons why those who do immigrate successfully tend to be healthier and mentally tougher than average. This is referred to, appropriately enough, as the healthy migrant hypothesis.
What is the healthy migrant hypothesis?
“The fundamental premise of the healthy migrant hypothesis is that the process of migration is not random," says Christopher P. Salas-Wright, the study's author. Instead, “individuals who are inclined to migrate, and able to do so successfully, are part of a uniquely healthy and psychologically hardy subset."
Essentially, immigrants appear to be healthier because only the healthy are capable of immigrating. Unhealthy individuals either lack the ability or desire to leave their home countries, while healthier individuals who voluntarily decide to immigrate better handle the stresses of doing so and are more mentally resilient in general.
Florence Thompson, a migrant mother with three of her seven children at a farm workers' camp in Nipomo, California. (Photo by Dorothea Lange/Getty Images)
The logistical and financial barriers to immigration are likely what prevents unhealthy individuals from making it to the U.S. In fact, when these barriers are removed, the rates of mental disorders in immigrants tends to rise to U.S. levels. Puerto Ricans, for example, can freely travel to the mainland U.S. without going through immigration. As it turns out, they have comparable levels of mental illness as individuals from the mainland.
“Notably," says Dr. Salas-Wright, “the logic here is mostly applicable to individuals who actively decide to migrate." When there is no choice but to migrate, as is the case with refugees, the research is a little less clear.
The survey used to collect the bulk of the data did not distinguish between what types of immigrants were interviewed, so this study could not comment on the specific differences between voluntary migrants (laborers, people who had immigrated to be with family, etc.) and involuntary migrants (refugees and asylum seekers). However, previous research has shown that refugees do experience higher levels of PTSD than non-refugee immigrants.
Dr. Salas-Wright's study did look at the different rates of mental health issues based on age. Nearly all age groups of immigrants experienced fewer mental health issues except for children under the age of 12. They were just as likely as U.S.-born individuals to experience a mental health disorder in their lives.
Honduran asylum seeker Daniel Once, age two, arrives to an immigrant shelter with his family on April 25, 2018 in Tijuana, Mexico. (Photo by John Moore/Getty Images)
Because they do not actively participate in the decision to leave their home countries, both healthy and unhealthy children immigrate, whereas an unhealthy adult may have decided to remain. However, the study also acknowledges that other factors may be in play when it comes to the mental health of young immigrants. One notable factor is acculturation.
When adjusting is unhealthy
Because children are still developing, they quickly adjust to new environments, such as a new country. Acculturation theory explains that immigrants who become more immersed in their adoptive culture—more acculturated—experience worse health outcomes than those who are less acculturated. For example, Hispanics in the U.S. who mostly speak Spanish and associate with other Spanish speakers are less likely to use drugs and eat fast food and are more likely to be physically active.
In addition, immigrants who quickly become acculturated also report higher rates of discrimination than less-acculturated immigrants, the stress of which may account for higher rates of mental health issues.
Ali Younes, an 8 year-old from Lebanon, sits with his mother after becoming a U.S. citizen during a citizenship ceremony at The Bronx Zoo, May 5, 2017 in New York City. (Photo by Drew Angerer/Getty Images)
Because children are still developing, they quickly become acculturated to U.S. culture and take on the same behaviors that result in mental illness in U.S.-born individuals. They also come into more contact with U.S.-born individuals and potential discriminatory behavior and acculturated immigrants—who typically possess superior language skills—are more capable of recognizing discrimination when it occurs.
Despite the fact that children under 12 tended to experience mental illness at similar rates to Americans, the study ultimately supports the healthy migrant hypothesis. The 36,000+ immigrants surveyed reported fewer mental health issues than U.S.-born individuals. Immigrating anywhere is a challenge, and immigrating to the U.S. is even more difficult. Deciding to make the journey at all, let alone successfully immigrating, takes some serious mental fortitude.
- Being American May Be a Hazard to Your Health | Big Think ›
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Geologists discover a rhythm to major geologic events.
- It appears that Earth has a geologic "pulse," with clusters of major events occurring every 27.5 million years.
- Working with the most accurate dating methods available, the authors of the study constructed a new history of the last 260 million years.
- Exactly why these cycles occur remains unknown, but there are some interesting theories.
Our hearts beat at a resting rate of 60 to 100 beats per minute. Lots of other things pulse, too. The colors we see and the pitches we hear, for example, are due to the different wave frequencies ("pulses") of light and sound waves.
Now, a study in the journal Geoscience Frontiers finds that Earth itself has a pulse, with one "beat" every 27.5 million years. That's the rate at which major geological events have been occurring as far back as geologists can tell.
A planetary calendar has 10 dates in red
Credit: Jagoush / Adobe Stock
According to lead author and geologist Michael Rampino of New York University's Department of Biology, "Many geologists believe that geological events are random over time. But our study provides statistical evidence for a common cycle, suggesting that these geologic events are correlated and not random."
The new study is not the first time that there's been a suggestion of a planetary geologic cycle, but it's only with recent refinements in radioisotopic dating techniques that there's evidence supporting the theory. The authors of the study collected the latest, best dating for 89 known geologic events over the last 260 million years:
- 29 sea level fluctuations
- 12 marine extinctions
- 9 land-based extinctions
- 10 periods of low ocean oxygenation
- 13 gigantic flood basalt volcanic eruptions
- 8 changes in the rate of seafloor spread
- 8 times there were global pulsations in interplate magmatism
The dates provided the scientists a new timetable of Earth's geologic history.
Tick, tick, boom
Credit: New York University
Putting all the events together, the scientists performed a series of statistical analyses that revealed that events tend to cluster around 10 different dates, with peak activity occurring every 27.5 million years. Between the ten busy periods, the number of events dropped sharply, approaching zero.
Perhaps the most fascinating question that remains unanswered for now is exactly why this is happening. The authors of the study suggest two possibilities:
"The correlations and cyclicity seen in the geologic episodes may be entirely a function of global internal Earth dynamics affecting global tectonics and climate, but similar cycles in the Earth's orbit in the Solar System and in the Galaxy might be pacing these events. Whatever the origins of these cyclical episodes, their occurrences support the case for a largely periodic, coordinated, and intermittently catastrophic geologic record, which is quite different from the views held by most geologists."
Assuming the researchers' calculations are at least roughly correct — the authors note that different statistical formulas may result in further refinement of their conclusions — there's no need to worry that we're about to be thumped by another planetary heartbeat. The last occurred some seven million years ago, meaning the next won't happen for about another 20 million years.
When we rely on the conscious mind alone, we lose; but when we listen to the body, we gain a winning edge.
- Our surroundings contain far more information than our conscious minds can process.
- Our non-conscious minds are constantly gathering information and identifying patterns.
- By being interoceptively attuned — that is, aware of the inner state of the body — we can tap into what our non-conscious mind is trying to tell us.
The following is an adapted excerpt from the book The Extended Mind. It is reprinted with permission of the author.
If you'd like to make smarter choices and sounder decisions — and who doesn't? — you might want to take advantage of a resource you already have close at hand: your interoception. Interoception is, simply stated, an awareness of the inner state of the body. Just as we have sensors that take in information from the outside world (retinas, cochleas, taste buds, olfactory bulbs), we have sensors inside our bodies that send our brains a constant flow of data from within. These sensations are generated in places all over the body — in our internal organs, in our muscles, even in our bones — and then travel via multiple pathways to a structure in the brain called the insula. Such internal reports are merged with several other streams of information — our active thoughts and memories, sensory inputs gathered from the external world — and integrated into a single snapshot of our present condition, a sense of "how I feel" in the moment, as well as a sense of the actions we must take to maintain a state of internal balance.
To understand the role interoception can play in smart decision-making, it's important to know that the world is full of far more information than our conscious minds can process. However, we are also able to collect and store the volumes of information we encounter on a non-conscious basis. As we proceed through each day, we are continuously apprehending and storing regularities in our experience, tagging them for future reference. Through this information-gathering and pattern-identifying process, we come to know things — but we're typically not able to articulate the content of such knowledge or to ascertain just how we came to know it. This trove of data remains mostly under the surface of consciousness, and that's usually a good thing. Its submerged status preserves our limited stores of attention and working memory for other uses.
A study led by cognitive scientist Pawel Lewicki demonstrates this process in microcosm. Participants in Lewicki's experiment were directed to watch a computer screen on which a cross-shaped target would appear, then disappear, then reappear in a new location; periodically they were asked to predict where the target would show up next. Over the course of several hours of exposure to the target's movements, the participants' predictions grew more and more accurate. They had figured out the pattern behind the target's peregrinations. But they could not put this knowledge into words, even when the experimenters offered them money to do so. The subjects were not able to describe "anything even close to the real nature" of the pattern, Lewicki observes. The movements of the target operated according to a pattern too complex for the conscious mind to accommodate — but the capacious realm that lies below consciousness was more than roomy enough to contain it.
"Nonconscious information acquisition," as Lewicki calls it, along with the ensuing application of such information, is happening in our lives all the time. As we navigate a new situation, we're scrolling through our mental archive of stored patterns from the past, checking for ones that apply to our current circumstances. We're not aware that these searches are under way; as Lewicki observes, "The human cognitive system is not equipped to handle such tasks on the consciously controlled level." He adds, "Our conscious thinking needs to rely on notes and flowcharts and lists of 'if-then' statements — or on computers — to do the same job which our non-consciously operating processing algorithms can do without external help, and instantly."
But — if our knowledge of these patterns is not conscious, how then can we make use of it? The answer is that, when a potentially relevant pattern is detected, it's our interoceptive faculty that tips us off: with a shiver or a sigh, a quickening of the breath or a tensing of the muscles. The body is rung like a bell to alert us to this useful and otherwise inaccessible information. Though we typically think of the brain as telling the body what to do, just as much does the body guide the brain with an array of subtle nudges and prods. (One psychologist has called this guide our "somatic rudder.") Researchers have even captured the body in mid-nudge, as it alerts its inhabitant to the appearance of a pattern that she may not have known she was looking for.
Such interoceptive prodding was visible during a gambling game that formed the basis of an experiment led by neuroscientist Antonio Damasio, a professor at the University of Southern California. In the game, presented on a computer screen, players were given a starting purse of two thousand "dollars" and were shown four decks of digital cards. Their task, they were told, was to turn the cards in the decks face-up, choosing which decks to draw from such that they would lose the least amount of money and win the most. As they started clicking to turn over cards, players began encountering rewards — bonuses of $50 here, $100 there — and also penalties, in which small or large amounts of money were taken away. What the experimenters had arranged, but the players were not told, was that decks A and B were "bad" — they held lots of large penalties in store — and decks C and D were "good," bestowing more rewards than penalties over time.
How Our Brains Feel Emotion | Antonio Damasio | Big Think www.youtube.com
As they played the game, the participants' state of physiological arousal was monitored via electrodes attached to their fingers; these electrodes kept track of their level of "skin conductance." When our nervous systems are stimulated by an awareness of potential threat, we start to perspire in a barely perceptible way. This slight sheen of sweat momentarily turns our skin into a better conductor of electricity. Researchers can thus use skin conductance as a measure of nervous system arousal. Looking over the data collected by the skin sensors, Damasio and his colleagues noticed something interesting: after the participants had been playing for a short while, their skin conductance began to spike when they contemplated clicking on the bad decks of cards. Even more striking, the players started avoiding the bad decks, gravitating increasingly to the good decks. As in the Lewicki study, subjects got better at the task over time, losing less and winning more.
Yet interviews with the participants showed that they had no awareness of why they had begun choosing some decks over others until late in the game, long after their skin conductance had started flaring. By card 10 (about forty-five seconds into the game), measures of skin conductance showed that their bodies were wise to the way the game was rigged. But even ten turns later — on card 20 — "all indicated that they did not have a clue about what was going on," the researchers noted. It took until card 50 was turned, and several minutes had elapsed, for all the participants to express a conscious hunch that decks A and B were riskier. Their bodies figured it out long before their brains did. Subsequent studies supplied an additional, and crucial, finding: players who were more interoceptively aware were more apt to make smart choices within the game. For them, the body's wise counsel came through loud and clear.
Damasio's fast-paced game shows us something important. The body not only grants us access to information that is more complex than what our conscious minds can accommodate. It also marshals this information at a pace that is far quicker than our conscious minds can handle. The benefits of the body's intervention extend well beyond winning a card game; the real world, after all, is full of dynamic and uncertain situations, in which there is no time to ponder all the pros and cons. When we rely on the conscious mind alone, we lose — but when we listen to the body, we gain a winning edge.
Annie Murphy Paul is a science writer who covers research on learning and cognition. She is the author of The Extended Mind: The Power of Thinking Outside the Brain, from which this article is adapted.
Brain cells snap strands of DNA in many more places and cell types than researchers previously thought.
The urgency to remember a dangerous experience requires the brain to make a series of potentially dangerous moves: Neurons and other brain cells snap open their DNA in numerous locations — more than previously realized, according to a new study — to provide quick access to genetic instructions for the mechanisms of memory storage.
The extent of these DNA double-strand breaks (DSBs) in multiple key brain regions is surprising and concerning, says study senior author Li-Huei Tsai, Picower Professor of Neuroscience at MIT and director of The Picower Institute for Learning and Memory, because while the breaks are routinely repaired, that process may become more flawed and fragile with age. Tsai's lab has shown that lingering DSBs are associated with neurodegeneration and cognitive decline and that repair mechanisms can falter.
"We wanted to understand exactly how widespread and extensive this natural activity is in the brain upon memory formation because that can give us insight into how genomic instability could undermine brain health down the road," says Tsai, who is also a professor in the Department of Brain and Cognitive Sciences and a leader of MIT's Aging Brain Initiative. "Clearly, memory formation is an urgent priority for healthy brain function, but these new results showing that several types of brain cells break their DNA in so many places to quickly express genes is still striking."
In 2015, Tsai's lab provided the first demonstration that neuronal activity caused DSBs and that they induced rapid gene expression. But those findings, mostly made in lab preparations of neurons, did not capture the full extent of the activity in the context of memory formation in a behaving animal, and did not investigate what happened in cells other than neurons.
In the new study published July 1 in PLOS ONE, lead author and former graduate student Ryan Stott and co-author and former research technician Oleg Kritsky sought to investigate the full landscape of DSB activity in learning and memory. To do so, they gave mice little electrical zaps to the feet when they entered a box, to condition a fear memory of that context. They then used several methods to assess DSBs and gene expression in the brains of the mice over the next half-hour, particularly among a variety of cell types in the prefrontal cortex and hippocampus, two regions essential for the formation and storage of conditioned fear memories. They also made measurements in the brains of mice that did not experience the foot shock to establish a baseline of activity for comparison.
The creation of a fear memory doubled the number of DSBs among neurons in the hippocampus and the prefrontal cortex, affecting more than 300 genes in each region. Among 206 affected genes common to both regions, the researchers then looked at what those genes do. Many were associated with the function of the connections neurons make with each other, called synapses. This makes sense because learning arises when neurons change their connections (a phenomenon called "synaptic plasticity") and memories are formed when groups of neurons connect together into ensembles called engrams.
"Many genes essential for neuronal function and memory formation, and significantly more of them than expected based on previous observations in cultured neurons … are potentially hotspots of DSB formation," the authors wrote in the study.
In another analysis, the researchers confirmed through measurements of RNA that the increase in DSBs indeed correlated closely with increased transcription and expression of affected genes, including ones affecting synapse function, as quickly as 10-30 minutes after the foot shock exposure.
"Overall, we find transcriptional changes are more strongly associated with [DSBs] in the brain than anticipated," they wrote. "Previously we observed 20 gene-associated [DSB] loci following stimulation of cultured neurons, while in the hippocampus and prefrontal cortex we see more than 100-150 gene associated [DSB] loci that are transcriptionally induced."
Snapping with stress
In the analysis of gene expression, the neuroscientists looked at not only neurons but also non-neuronal brain cells, or glia, and found that they also showed changes in expression of hundreds of genes after fear conditioning. Glia called astrocytes are known to be involved in fear learning, for instance, and they showed significant DSB and gene expression changes after fear conditioning.
Among the most important functions of genes associated with fear conditioning-related DSBs in glia was the response to hormones. The researchers therefore looked to see which hormones might be particularly involved and discovered that it was glutocortocoids, which are secreted in response to stress. Sure enough, the study data showed that in glia, many of the DSBs that occurred following fear conditioning occurred at genomic sites related to glutocortocoid receptors. Further tests revealed that directly stimulating those hormone receptors could trigger the same DSBs that fear conditioning did and that blocking the receptors could prevent transcription of key genes after fear conditioning.
Tsai says the finding that glia are so deeply involved in establishing memories from fear conditioning is an important surprise of the new study.
"The ability of glia to mount a robust transcriptional response to glutocorticoids suggest that glia may have a much larger role to play in the response to stress and its impact on the brain during learning than previously appreciated," she and her co-authors wrote.
Damage and danger?
More research will have to be done to prove that the DSBs required for forming and storing fear memories are a threat to later brain health, but the new study only adds to evidence that it may be the case, the authors say.
"Overall we have identified sites of DSBs at genes important for neuronal and glial functions, suggesting that impaired DNA repair of these recurrent DNA breaks which are generated as part of brain activity could result in genomic instability that contribute to aging and disease in the brain," they wrote.
The National Institutes of Health, The Glenn Foundation for Medical Research, and the JPB Foundation provided funding for the research.
Research shows that those who spend more time speaking tend to emerge as the leaders of groups, regardless of their intelligence.