Source: Harvard University
For immediate release: September 5, 2019
Boston, MA – Women who experienced six or more symptoms of post-traumatic stress disorder (PTSD) at some point in life had a twofold greater risk of developing ovarian cancer compared with women who never had any PTSD symptoms, according to a new study from researchers at Harvard T.H. Chan School of Public Health and Moffitt Cancer Center.
The findings indicate that having higher levels of PTSD symptoms, such as being easily startled by ordinary noises or avoiding reminders of the traumatic experience, can be associated with increased risks of ovarian cancer even decades after women experience a traumatic event. The study also found that the link between PTSD and ovarian cancer remained for the most aggressive forms of ovarian cancer.
The study was published in Cancer Research, on September 5, 2019.
“In light of these findings, we need to understand whether successful treatment of PTSD would reduce this risk, and whether other types of stress are also risk factors for ovarian cancer,” said co-author Andrea Roberts, research scientist at Harvard T.H. Chan School of Public Health.
Ovarian cancer is the deadliest gynecologic cancer and the fifth most common cause of cancer-related death among U.S. women. Studies in animal models have shown that stress and stress hormones can accelerate ovarian tumor growth, and that chronic stress can result in larger and more invasive tumors. A prior study found an association between PTSD and ovarian cancer in humans, but the study included only seven women with ovarian cancer and PTSD.
“Ovarian cancer has been called a ‘silent killer’ because it is difficult to detect in its early stages; therefore identifying more specifically who may be at increased risk for developing the disease is important for prevention or earlier treatment,” said co-author Laura Kubzansky, Lee Kum Kee Professor of Social and Behavioral Sciences at Harvard Chan School.
To better understand how PTSD may influence ovarian cancer risk, researchers analyzed data from the Nurses’ Health Study II, which tracked the health of tens of thousands of women between 1989 and 2015 through biennial questionnaires and medical records. Participants were asked about ovarian cancer diagnosis on each questionnaire, and information was validated through a review of medical records.
In 2008, 54,763 Nurses’ Health Study II participants responded to a supplemental questionnaire focused on lifetime traumatic events and symptoms associated with those events. Women were asked to identify the event they considered the most stressful, and the year of this event. They were also asked about seven PTSD symptoms they may have experienced related to the most stressful event.
Based on the responses, women were divided into six groups: no trauma exposure; trauma and no PTSD symptoms; trauma and 1-3 symptoms; trauma and 4-5 symptoms; trauma and 6-7 symptoms; and trauma, but PTSD symptoms unknown.
After adjusting for various factors associated with ovarian cancer, including oral contraceptive use and smoking, the researchers found that women who experienced 6-7 symptoms associated with PTSD were at a significantly higher risk for ovarian cancer than women who had never been exposed to trauma. Women with trauma and 4-5 symptoms were also at an elevated risk, but the risk did not reach statistical significance.
The study also showed that women who experienced 6-7 symptoms associated with PTSD were at a significantly higher risk of developing the high-grade serous histotype of ovarian cancer—the most common and aggressive form of the disease.
“Ovarian cancer has relatively few known risk factors – PTSD and other forms of distress, like depression, may represent a novel direction in ovarian cancer prevention research,” said Shelley Tworoger, associate center director of population science at Moffitt. “If confirmed in other populations, this could be one factor that doctors could consider when determining if a woman is at high risk of ovarian cancer in the future.”
Other Harvard Chan School researchers who contributed to the study included Karestan Koenen and Yongjoo Kim. Tianyi Huang of Brigham and Women’s Hospital and Harvard Medical School was also a co-author.
Funding for this study came from DOD grant W81XWH-17-1-0153.
“Posttraumatic stress disorder (PTSD) is associated with increased risk of
ovarian cancer: a prospective and retrospective longitudinal cohort study,” Andrea
L. Roberts, Tianyi Huang, Karestan C. Koenen, Yongjoo Kim, Laura D. Kubzansky,
Shelley S. Tworoger, Cancer Research, online September 5, 2019 doi:
10.1158/0008-5472.CAN-19-1222
Source: Harvard University
Gingivitis (gum disease) has been linked to a higher risk of heart disease, but a recent study says that the bacteria that cause gingivitis also may be connected to Alzheimer's disease. The study was published Jan. 23, 2019, in Science Advances.
Scientists have previously found that this species of bacteria, called Porphyromonas gingivalis, can move from the mouth to the brain. Once in the brain, the bacteria release enzymes called gingipains that can destroy nerve cells, which in turn can lead to memory loss and eventually Alzheimer's.
In this study, researchers looked for evidence of this process in human brains. They examined the brains of 53 deceased people who had been diagnosed with Alzheimer's and found high levels of gingipain in almost all of them. They also noted that the amount of gingipain tended to rise over time, which suggests there may be a tipping point when dementia symptoms first begin.
The next research step is to see if a drug can block these harmful
bacterial enzymes and possibly stop Alzheimer's from developing or at
least slow its progression. Until then, you can do your part by fighting
gingivitis with strong oral health habits, including daily flossing and
brushing twice a day and staying current on regular dental check-ups.
Source: Harvard University
Artificial light at night may lead to weight gain
Published: September, 2019
If you leave lights shining or keep the television on while you sleep, it could affect your waistline, according to a study published online June 10 by JAMA Internal Medicine. The study found an association between exposure to artificial light during sleep and weight gain in women.
The research team looked at questionnaires completed by more than 40,000 women, which asked, among other things, whether the women slept with lights on nearby or in the same room. The researchers also recorded the women's height, body mass index (a measure of weight in relation to height), and waist size at the time they entered the study and then five years later. They found that women who slept with a light or television on in the room were 17% more likely to have gained 11 pounds or more during the course of the study. They did not find a similar effect when women used a small night light or had a light on outside the room that shone in. It's not clear why exposure to artificial light was linked with weight gain, but researchers speculated that it might affect sleep quality.
Source: University of Cambridge
People genetically predisposed to sleep problems have greater risk of heart failure and stroke, say researchers. People who struggle with sleep might be at greater risk of developing cardiovascular problems, research suggests.
Scientists have found that people who are genetically predisposed to insomnia have a greater risk of heart failure, stroke and coronary artery disease.
Researchers say the study backs previous work that has found links between poor sleep and cardiovascular problems, with the latest study supporting the idea that insomnia could play a role in causing such conditions.
“If that really is the case, then if we can improve or reduce sleep disturbances, that might reduce the risk of stroke,” said Prof Hugh Markus, co-author of the research from the University of Cambridge.
The new study relies on previous findings that there are about 250 genetic variants, each of which slightly increases the risk of someone having insomnia.
“Most people don’t have all of them, people will have a number of them, a few or many of them,” said Markus.
The crucial point is the way the genetic variants are inherited. Whether an individual carries them is random: their presence does not depend on the rest of that person’s genetic makeup or environmental factors, such as where they live, their wealth or how much they exercise.
That means it is theoretically possible to look at whether an increased risk of insomnia could play a role in causing stroke, heart failure and coronary artery disease, while reducing the impact of other factors that can muddy the waters. This is a different approach to previous studies which could only show association, not causation.
Writing in the journal Circulation, researchers from the UK and Sweden report how they harnessed this approach by drawing on health and genetic information within a range of large-scale databases.
For each cardiovascular condition, data from hundreds of thousands of individuals was examined – for investigations into heart failure the team used data from almost 400,000 participants in the UK Biobank study alone.
While Markus noted it was not yet clear whether improving insomnia would improve cardiovascular health, he said there were interventions that could help those who struggle to sleep, including cognitive behavioural therapy.
However, the latest study had limitations including that it only looked at genetic predisposition to insomnia, rather than how much sleep individuals actually managed per night, and that the majority of the data was gathered from people with European ancestry.
Michael Holmes, of the University of Oxford, who is an expert in using genetics to unpick disease risk, urged caution, saying it was not clear whether sleep loss arising from the genetic variants increased the risk of cardiovascular disease, or whether the link was down to the genetic variants triggering other effects.
He said: “This study doesn’t allow us to conclude that insomnia causes cardiovascular disease. Rather, all we can say is that individuals carrying genetic variants linked to a higher risk of insomnia also have a higher risk of cardiovascular disease.”
Prof Jeremy Pearson, associate medical director at the British Heart Foundation, said: “People who suffer from insomnia or disturbed sleep are often at increased risk of coronary heart disease – the leading cause of a heart attack. But it’s hard to know whether there’s a direct connection or if this is down to other behaviours that are common among people who struggle to sleep, such as a poor diet or living with high blood pressure.
“This study suggests that people whose genetic makeup predisposes them to insomnia also have a slightly increased risk of coronary heart disease. If this connection is proven in further research, it could pave the way for more precise ways of lowering the risk of heart disease in people who suffer from insomnia.”
Source: Stanford University
Matchmaking
is now the primary job of online algorithms, according to new research from
Stanford sociologist Michael Rosenfeld. His new study shows that most
heterosexual couples today meet online.
Algorithms, and not friends and
family, are now the go-to matchmaker for people looking for love, Stanford
sociologist Michael Rosenfeld has found.
Online dating has become the most
common way for Americans to find romantic partners. (Cover image credit: altmodern /
Getty Images)
In a new study published in the Proceedings of the National Academy of Sciences, Rosenfeld found that heterosexual couples are more likely to meet a romantic partner online than through personal contacts and connections. Since 1940, traditional ways of meeting partners – through family, in church and in the neighborhood – have all been in decline, Rosenfeld said.
Rosenfeld, a lead author on the research and a professor of sociology in the School of Humanities and Sciences, drew on a nationally representative 2017 survey of American adults and found that about 39 percent of heterosexual couples reported meeting their partner online, compared to 22 percent in 2009. Sonia Hausen, a graduate student in sociology, was a co-author of the paper and contributed to the research.
Rosenfeld has studied mating and dating as well as the internet’s effect on society for two decades.
Stanford News Service interviewed Rosenfeld about his research.
What’s the main takeaway from your research on online dating?
Meeting a significant other online has replaced meeting through friends. People trust the new dating technology more and more, and the stigma of meeting online seems to have worn off.
In 2009, when I last researched how people find their significant others, most people were still using a friend as an intermediary to meet their partners. Back then, if people used online websites, they still turned to friends for help setting up their profile page. Friends also helped screen potential romantic interests.
What were you surprised to find?
I was surprised at how much online dating has displaced the help of friends in meeting a romantic partner. Our previous thinking was that the role of friends in dating would never be displaced. But it seems like online dating is displacing it. That’s an important development in people’s relationship with technology.
What do you believe led to the shift in how people meet their significant other?
There are two core technological innovations that have each elevated online dating. The first innovation was the birth of the graphical World Wide Web around 1995. There had been a trickle of online dating in the old text-based bulletin board systems prior to 1995, but the graphical web put pictures and search at the forefront of the internet. Pictures and search appear to have added a lot to the internet dating experience. The second core innovation is the spectacular rise of the smart phone in the 2010s. The rise of the smart phone took internet dating off the desktop and put it in everyone’s pocket, all the time.
Also, the online dating systems have much larger pools of potential partners compared to the number of people your mother knows, or the number of people your best friend knows. Dating websites have enormous advantages of scale. Even if most of the people in the pool are not to your taste, a larger choice set makes it more likely you can find someone who suits you.
Does your finding indicate that people are increasingly less social?
No. If we spend more time online, it does not mean we are less social.
When it comes to single people looking for romantic partners, the online dating technology is only a good thing, in my view. It seems to me that it’s a basic human need to find someone else to partner with and if technology is helping that, then it’s doing something useful.
The decline of meeting partners through family isn’t a sign that people don’t need their family anymore. It’s just a sign that romantic partnership is taking place later in life.
In addition, in our study we found that the success of a relationship did not depend on whether the people met online or not. Ultimately, it doesn’t matter how you met your significant other, the relationship takes a life of its own after the initial meeting.
What does your research reveal about the online world?
I think that internet dating is a modest positive addition to our world. It is generating interaction between people that we otherwise wouldn’t have.
People who have in the past had trouble finding a potential partner benefit the most from the broader choice set provided by the dating apps.
Internet dating has the potential to serve people who were ill-served by family, friends and work. One group of people who was ill-served was the LGBTQ+ community. So the rate of gay couples meeting online is much higher than for heterosexual couples.
You’ve studied dating for over two decades. Why did you decide to research online dating?
The landscape of dating is just one aspect of our lives that is being affected by technology. And I always had a natural interest in how new technology was overturning the way we build our relationships.
I was curious how couples meet and
how has it changed over time. But no one has looked too deeply into that
question, so I decided to research it myself.
Source: Harvard University
That said, certain foods in this overall scheme are particularly rich in healthful components like omega-3 fatty acids, B vitamins, and antioxidants, which are known to support brain health and often referred to as foods. Incorporating many of these foods into a healthy diet on a regular basis can improve the health of your brain, which could translate into better mental function.
Research shows that the best brain foods are the same ones that protect your heart and blood vessels, including the following:
Source: University of Oxford
A global study of 12 million people has found diabetes increases the risk of heart failure and this increase is greater for women than men. Researchers from The George Institute for Global Health determined that this differential was greater in type 1 than type 2 diabetes. Type 1 diabetes is associated with a 47% excess risk of heart failure in women compared to men, whilst type 2 diabetes has a 9% higher excess risk of heart failure for women than men.
The findings published in Diabetologia (the journal of the European Association for the Study of Diabetes [EASD]) highlights the need for further sex-specific research into diabetes and how the condition can potentially contribute to heart complications.
According to the International Diabetes Federation (IDF), currently 415 million adults world-wide live with diabetes – with approximately 199 million of them being women. The IDF expects by the year 2040 around 313 million women will be suffering from the disease. Diabetes is the ninth leading cause of death in women and claims 2.1 million female lives every year, more so than men. The number one leading cause of death for women is heart disease.
'It is already known that diabetes puts you at greater risk of developing heart failure but what our study shows for the first time is that women are at far greater risk – for both type 1 and type 2 diabetes,' said lead author and research fellow Dr Toshiaki Ohkuma from The George Institute.
'The increased risk of heart failure following a diabetes diagnosis is significantly greater in women than men which highlights the importance of intensive prevention and treatment of diabetes in women. Further research is required to understand the mechanisms underpinning the excess risk of heart failure conferred by diabetes [particularly type 1] in women and to reduce the burden associated with diabetes in both sexes.'
Key findings:
• Women with type 1 diabetes were associated with a more than 5-fold
increased risk of heart failure compared with those without diabetes. For
men, the risk was 3.5-fold higher.
• Corresponding increases in risks for heart failure associated with type 2
diabetes were 95% in women and 74% in men.
• Researchers also found that both type 1 and type 2 diabetes were stronger
risk factors for heart failure in women than men.
• Type 1 diabetes was associated with a 47% greater excess risk of heart
failure in women compared with men.
• Type 2 diabetes was associated with a 9% greater excess risk of heart failure
in women than men.
*Data compiled from 10 countries: Australia, US, UK, Italy, Sweden, Canada,
Japan, China, Taiwan and Korea.
According to Diabetes Australia, the prevalence of diabetes is now so widespread that it has become the major health crisis of the 21st Century. It is the largest challenge facing the Australian health system with around 1.7 million sufferers nationwide. More than 119,000 Australians are living with type 1 diabetes, an autoimmune condition, whereas 1.3 million Australians are living with type 2 diabetes, the effects of which can be exacerbated by lifestyle factors such as poor diet and lack of exercise. It’s estimated that the number of people suffering from diabetes globally will increase to 642 million by 2040.
Study co-author Dr Sanne Peters, of The George Institute for Global Health
at the University of Oxford, said there are a number of reasons why women with
diabetes are at greater risk of heart complications. 'Women were reported to have two years’ longer duration of prediabetes
than men and this increased duration may be associated with greater excess risk
of heart failure in women' said Dr Peters.
'Some major concerns are that women are also being undertreated for diabetes, are not taking the same levels of medications as men and are less likely to receive intensive care.'
The IDF reports that girls and women with diabetes experience a range of
challenges. Gender roles, power imbalances, socioeconomic inequalities
resulting in poor diet and lack of physical activity can all influence
vulnerability to diabetes.
Women’s limited access to health services and lack of pro-activity when it comes to seeking treatment for health problems can also amplify the impact of diabetes, particularly in developing countries.
Diabetes is one of the leading causes of cardiovascular disease, blindness, kidney failure and lower-limb amputation. In pregnancy, poorly controlled diabetes increases the risk of maternal and foetal complications. Women with type 2 diabetes also have a significantly increased risk of depression in comparison to men.
The George Institute has been leading gender specific research and has already shown women with diabetes have a significantly greater excess risk of stroke and coronary heart disease as well as the non-cardiovascular complications of dementia and cancer than men. It is currently investigating gender differences in stroke as well as other chronic diseases.
The full paper, Diabetes as a risk factor for heart failure in women and men: a systematic review and meta-analysis of 47 cohorts including 12 million individuals can be read in Diabetologia.
Some people over age 60 have few, if any, classic
hypothyroidism symptoms, while others experience the same symptoms younger
people do. Still others have hypothyroidism symptoms that are not typical at
all, making the diagnosis even more difficult. Any of the following signs and
symptoms can indicate hypothyroidism in an older person.
Unexplained high cholesterol. High cholesterol is sometimes
the only evidence of an underactive thyroid in an older person. The problem
might be diagnosed as a cholesterol disorder rather than hypothyroidism.
Because this sign may stand alone, high cholesterol warrants a thyroid
evaluation.
Heart failure. Reduced blood volume, weaker contractions of the heart muscle, and a slower heart rate—all caused by low thyroid hormone levels—can contribute to heart failure, a serious condition that occurs when your heart can't pump out enough blood to meet the needs of your body. The ineffective pumping also causes blood to back up in the veins that return blood to the heart. Blood backs up all the way into the lungs, which causes them to become congested with fluid. Symptoms of heart failure include breathlessness, swelling in the ankles, weakness, and fatigue.
Bowel movement changes. An older person with hypothyroidism
might have constipation because stool moves more slowly through the bowels. A
less common hypothyroidism symptom is frequent bouts of diarrhea—a problem more
typically associated with hyperthyroidism. Some people with an autoimmune
thyroid disease such as Hashimoto's also have celiac disease, another
autoimmune condition that can cause diarrhea.
Joint or muscle pain. Vague joint pain is a classic hypothyroidism symptom. It sometimes is the only symptom of hypothyroidism in an older person. Many people experience general muscle aches, particularly in large muscle groups like those in the legs.
Psychiatric problems. Clinical depression—a common symptom
in younger people with hypothyroidism—can also affect older people with the
condition. The difference is that in older people it can be the only
hypothyroidism symptom. Some older adults also develop psychosis with
delusional behavior or hallucinations.
Dementia. Debilitating memory loss that is often, but not
always, accompanied by depression or psychosis can also be the lone symptom of
hypothyroidism. If you or a loved one is being evaluated for dementia, make
sure that a thyroid test is part of the evaluation.
Balance problems. Hypothyroidism can lead to abnormalities
in the cerebellum (a region at the back of the brain that's involved in motor
control). This may cause problems with walking in older people.
Source: Cornell University College of Veterinary Medicine
The Special Needs of the Senior Cat
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Just as people are living longer
than they did in the past, cats are living longer too, and there is every
reason to expect that the "graying" cat population will continue to
grow.
How old is my cat in human years?
Cats are individuals and, like people, they experience advancing years in their
own unique ways. Many cats begin to encounter age-related physical changes
between seven and ten years of age, and most do so by the time they are 12. The
commonly held belief that every "cat year" is worth seven "human
years" is not entirely accurate. In reality, a one-year-old cat is
physiologically similar to a 16-year-old human, and a two-year-old cat is like
a person of 21. For every year thereafter, each cat year is worth about four
human years. Using this formula, a ten-year-old cat is similar age wise to a
53-year-old person, a 12-year-old cat to a 61-year-old person, and a
15-year-old cat to a person of 73.
Advancing age is not a disease
Aging is a natural process. Although many complex
physical changes accompany advancing years, age in and of itself is not a
disease. Even though many conditions that affect older cats are not
correctable, they can often be controlled. The key to making sure your senior
cat has the healthiest and highest quality of life possible is to recognize and
reduce factors that may be health risks, detect disease as early as possible,
correct or delay the progression of disease, and improve or maintain the health
of the body's systems.
What happens as my cat ages?
The aging process is accompanied by many physical and behavioral changes:
Is my cat sick, or is it just old age?
Never assume that changes you see in your older cat are simply due to old age,
and are therefore untreatable. Owners of older cats often notice changes in
their cat's behavior, but consider these changes an inevitable and untreatable
result of aging. However, any alteration in your cat's behavior or physical
condition should alert you to contact your veterinarian.
Disease of virtually any organ system, or any condition that causes pain or impairs mobility can contribute to changes in behavior. For example:
How can I help keep my senior cat healthy?
Close observation is one of the most important tools you have to help keep your
senior cat healthy. You may wish to perform a basic physical examination on a
weekly basis. Ask your veterinarian to show you how to do it and what to look
for. You will find it easier if you just make the examination an extension of
the way you normally interact with your cat. For example, while you are rubbing
your cat's head or scratching its chin, gently raise the upper lips with your
thumb or forefinger so you can examine the teeth and gums. In the same way, you
can lift the ear flaps and examine the ear canals. While you are stroking your
cat's fur, you can check for abnormal lumps or bumps, and evaluate the health
of the skin and coat.
Daily Brushing
Daily brushing or combing removes loose hairs, preventing them from being
swallowed and forming hairballs. Brushing also stimulates blood circulation and
sebaceous gland secretions, resulting in a healthier skin and coat. Older cats
may not use scratching posts as frequently as they did when they were younger;
therefore, nails should be checked weekly and trimmed if necessary.
Daily Tooth Brushing
Brushing your cat's teeth with a pet-specific toothpaste or powser is the
single most effective way to prevent dental disease. Dental disease is more
common in older cats and can lead to other health problems, so maintaining oral
health is important. Most cats will allow their teeth to be brushed, although
it may be necessary to gradually introduce your cat to tooth brushing over
several weeks to months. Watch this video for
instructions on how to brush your cat's teeth.
Proper Nutrition
Many cats get heavier or even obese as they age. If your cat is overweight, you
should ask your veterinarian to help you modify the diet so that a normal body condition
can be restored. Other cats actually become too thin as they get older. Weight
loss can be caused by a variety of medical problems such as kidney failure, and
special diets may be helpful in managing these problems.
Reducing Stress
Reducing environmental stress whenever possible is very important since older
cats are usually less adaptable to change. Special provisions should be made
for older cats that must be boarded for a period of time. Having a familiar
object, such as a blanket or toy, may prevent the cat from becoming too
distraught in a strange environment. A better alternative is to have the older
cat cared for at home by a neighbor, friend, or relative. Introducing a new pet
may be a traumatic experience for older cats, and should be avoided whenever
possible. Moving to a new home can be equally stressful, however, stress can be
alleviated by giving the older cat more affection and attention during times of
emotional upheaval.
Cats are experts at hiding illness, and elderly cats are no exception. It is common for a cat to have a serious medical problem, yet not show any sign of it until the condition is quite advanced. Since most diseases can be managed more successfully when detected and treated early in their course, it is important for owners of senior cats to carefully monitor their behavior and health.
How can my veterinarian help?
Just as your observations can help detect disease in the early stages, so too
can regular veterinary examinations. Your veterinarian may suggest evaluating
your healthy senior cat more frequently than a younger cat. If your cat has a
medical condition, more frequent evaluations may also be necessary. During your
cat's examination, the veterinarian will gather a complete medical and
behavioral history, perform a thorough physical examination in order to
evaluate every organ system, check your cat's weight and body condition, and
compare them to previous evaluations. At least once a year, certain tests,
including blood tests, fecal examination, and urine analysis, may be suggested.
In this way, disorders can be found and treated early, and ongoing medical
conditions can be appraised. Both are necessary to keep your senior cat in the
best possible health.
Should I adopt an older cat?
A special group of senior cats that deserves particular attention is older cats
in shelters. While young cats and kittens are attractive to most potential
adopters due to their cuteness and playfulness, senior cats are often
overlooked by people considering adopting a cat. If people keep their minds
open, they will find that there are countless older cats that would make
excellent pets and would brighten up any home. Older cats in shelters are often
more calm, are more likely to be litter trained, and can provide wonderful
companionship to anyone kind enough to take them into their home. The next time
you are at the shelter, take some time to check out these mature felines.
Taking them home can make both of your lives richer, happier, and more
satisfying.
Probiotics can do more than improve your gut health. They also may indirectly enhance your brain, too.
Research shows that the gut and brain are connected, a partnership called the gut-brain axis. The two are linked through biochemical signaling between the nervous system in the digestive tract, called the enteric nervous system, and the central nervous system, which includes the brain. The primary information connection between the brain and gut is the vagus nerve, the longest nerve in the body.
The gut has been called a "second brain" because it produces many of the same neurotransmitters as the brain does, like serotonin, dopamine, and gamma-aminobutyric acid, all of which play a key role in regulating mood. In fact, it is estimated that 90% of serotonin is made in the digestive tract.
What affects the gut often affects the brain and vice versa. When your brain senses trouble—the fight-or-flight response—it sends warning signals to the gut, which is why stressful events can cause digestive problems like a nervous or upset stomach. On the flip side, flares of gastrointestinal issues like irritable bowel syndrome (IBS), Crohn's disease, or chronic constipation may trigger anxiety or depression.
The brain-gut axis works in other ways, too. For example, your gut helps regulate appetite by telling the brain when it's time to stop eating. About 20 minutes after you eat, gut microbes produce proteins that can suppress appetite, which coincides with the time it often takes people to begin feeling full.
How might probiotics fit in the gut-brain axis? Some research has found that probiotics may help boost mood and cognitive function and lower stress and anxiety. For example, a study published online Nov. 10, 2016, by Frontiers in Aging Neuroscience found that Alzheimer's patients who took milk made with four probiotic bacteria species for 12 weeks scored better on a test to measure cognitive impairment compared with those who drank regular milk.
A small 2013 study reported in the journal Gastroenterology found that women who ate yogurt with a mix of probiotics, twice a day for four weeks, were calmer when exposed to images of angry and frightened faces compared with a control group. MRIs also found that the yogurt group had lower activity in the insula, the brain area that processes internal body sensations like those emanating from the gut.
It's too early to determine the exact role probiotics play in the gut-brain axis since this research is still ongoing. Probiotics may not only support a healthier gut, but a healthier brain, too.