A Breakthrough Global Study of Depression Finds 44 Genetic Variants Linked to the Disease

iStock
iStock

Though depression affects an estimated 14 percent of the world’s population, scientists know very little about the underlying causes of the disorder, and that makes it incredibly difficult to treat. Even now, researchers are still debating whether common antidepressant medications even work at all, and if they do, why.

New research published in the journal Nature Genetics provides a big step in figuring out why some people suffer from depression while others don’t, identifying 44 genetic variants that are risk factors for major depression, 30 of which are new. They also found two regions of the brain that appear to be associated with the development of the disorder.

The study is the result of an international effort by more than 200 researchers involved with the Psychiatric Genomics Consortium. It looked at more than 135,000 cases of depression (both self-reported and clinically assessed) and almost 345,000 control cases. It’s the largest study on the genetic basis of depression ever done.

The researchers found that all humans carry some of the 44 risk factors identified. Some people carry more than others, putting them at greater risk for developing depression. They also identified the prefrontal and anterior cingulate cortices (both located at the front of the brain) as the regions of the brain probably linked with the development of depression.

Some of the risk factors the researchers identified are also involved in other psychiatric disorders, like schizophrenia, which isn't entirely surprising—a 2007 study from the Psychiatric Genomics Consortium found that people with depression, bipolar disorder, and schizophrenia as well as developmental disorders like ADHD and autism share the same variations in four locations in their genetic code.

By identifying genetic risk factors associated with major depressive disorder, the scientists hope to increase our understanding of why depression strikes some people and not others. "[M]ajor depression is a brain disorder," the researchers conclude. "Although this is not unexpected, some past models of [major depressive disorder] have had little or no place for heredity or biology." They firmly put to rest the idea that depression is entirely a matter of environment.

Environment certainly plays a role—the researchers found links between lower education levels and higher body mass index and depression risk as well—but genetics may impact whether someone whose circumstances put them at risk of depression actually develops the disorder. Depression is still highly stigmatized, which often prevents people from seeking treatment for it, according to several studies. Further understanding of the genetic underpinnings of the disorder may help counter negative perceptions of depression as a character flaw or a sign of laziness.

The study could eventually change how doctors treat depression. Many of the genetic variants identified by this study are linked to targets of current antidepressant medications, like serotonin. But the research may also lead to the development of new medications and therapies that could work for more people (current medications don't work for everyone) and potentially have fewer side effects than existing treatments.

The study partially relied on self-reported depression diagnoses, meaning there's some wiggle room in knowing whether those people are actually clinically depressed to the degree that a medical professional would diagnose. Further research will need to confirm that these genetic variants are indeed linked to depression. There are likely even more gene variants related to depression risk, as well, but they might have too small of an effect to be identified by this study. The researchers hope to continue their work to understand the links between environmental stressors, genetic variations, and depression risk in the future.

12 Intriguing Facts About the Intestines

When we talk about the belly, gut, or bowels, what we're really talking about are the intestines—long, hollow, coiled tubes that comprise a major part of the digestive tract, running from the stomach to the anus. The intestines begin with the small intestine, divided into three parts whimsically named the duodenum, jejunum, and ileum, which absorb most of the nutrients from what we eat and drink. Food then moves into the large intestine, or colon, which absorbs water from the digested food and expels it into the rectum. That's when sensitive nerves in your rectum create the sensation of needing to poop.

These organs can be the source of intestinal pain, such as in irritable bowel syndrome, but they can also support microbes that are beneficial to your overall health. Here are some more facts about your intestines.

1. The intestines were named by medieval anatomists.

Medieval anatomists had a pretty good understanding of the physiology of the gut, and are the ones who gave the intestinal sections their names, which are still used today in modern anatomy. When they weren't moralizing about the organs, they got metaphorical about them. In 1535, the Spanish doctor Andrés Laguna noted that because the intestines "carry the chyle and all the excrement through the entire region of the stomach as if through the Ocean Sea," they could be likened to "those tall ships which as soon as they have crossed the ocean come to Rouen with their cargoes on their way to Paris but transfer their cargoes at Rouen into small boats for the last stage of the journey up the Seine."

2. Leonardo da Vinci believed the intestines helped you breathe.

Leonardo mistakenly believed the digestive system aided respiratory function. In 1490, he wrote in his unpublished notebooks, "The compressed intestines with the condensed air which is generated in them, thrust the diaphragm upwards; the diaphragm compresses the lungs and expresses the air." While that isn't anatomically accurate, it is true that the opening of the lungs is helped by the relaxation of stomach muscles, which does draw down the diaphragm.

3. Your intestines could cover two tennis courts ...

Your intestines take up a whole lot of square footage inside you. "The surface area of the intestines, if laid out flat, would cover two tennis courts," Colby Zaph, a professor of immunology in the department of biochemistry and molecular biology at Melbourne's Monash University, tells Mental Floss. The small intestine alone is about 20 feet long, and the large intestine about 5 feet long.

4. ... and they're pretty athletic.

The process of moving food through your intestines requires a wave-like pattern of muscular action, known as peristalsis, which you can see in action during surgery in this YouTube video.

5. Your intestines can fold like a telescope—but that's not something you want to happen.

Intussusception is the name of a condition where a part of your intestine folds in on itself, usually between the lower part of the small intestine and the beginning of the large intestine. It often presents as severe intestinal pain and requires immediate medical attention. It's very rare, and in children may be related to a viral infection. In adults, it's more commonly a symptom of an abnormal growth or polyp.

6. Intestines are very discriminating.

"The intestines have to discriminate between good things—food, water, vitamins, good bacteria—and bad things, such as infectious organisms like viruses, parasites and bad bacteria," Zaph says. Researchers don't entirely know how the intestines do this. Zaph says that while your intestines are designed to keep dangerous bacteria contained, infectious microbes can sometimes penetrate your immune system through your intestines.

7. The small intestine is covered in "fingers" ...

The lining of the small intestine is blanketed in tiny finger-like protrusions known as villi. These villi are then covered in even tinier protrusions called microvilli, which help capture food particles to absorb nutrients, and move food on to the large intestine.

8. ... And you can't live without it.

Your small intestine "is the sole point of food and water absorption," Zaph says. Without it, "you'd have to be fed through the blood."

9. The intestines house your microbiome. 

The microbiome is made up of all kinds of microorganisms, including bacteria, viruses, fungi, and protozoans, "and probably used to include worm parasites too," says Zaph. So in a way, he adds, "we are constantly infected with something, but it [can be] helpful, not harmful."

10. Intestines are sensitive to change.

Zaph says that many factors change the composition of the microbiome, including antibiotics, foods we eat, stress, and infections. But in general, most people's microbiomes return to a stable state after these events. "The microbiome composition is different between people and affected by diseases. But we still don't know whether the different microbiomes cause disease, or are a result in the development of disease," he says.

11. Transferring bacteria from one gut to another can transfer disease—or maybe cure it.

"Studies in mice show that transplanting microbes from obese mice can transfer obesity to thin mice," Zaph says. But transplanting microbes from healthy people into sick people can be a powerful treatment for some intestinal infections, like that of the bacteria Clostridium difficile, he adds. Research is pouring out on how the microbiome affects various diseases, including multiple sclerosis, Parkinson's, and even autism.

12. The microbes in your intestines might influence how you respond to medical treatments.

Some people don't respond to cancer drugs as effectively as others, Zaph says. "One reason is that different microbiomes can metabolize the drugs differently." This has huge ramifications for chemotherapy and new cancer treatments called checkpoint inhibitors. As scientists learn more about how different bacteria metabolize drugs, they could possibly improve how effective existing cancer treatments are.

This 3D-Printed Sushi is Customized For You Based on the Biological Sample You Send In

Open Meals
Open Meals

Many high-end restaurants require guests to make a reservation before they dine. At Sushi Singularity in Tokyo, diners will be asked to send fecal samples to achieve the ideal experience. As designboom reports, the new sushi restaurant from Open Meals creates custom sushi recipes to fit each customer's nutritional needs.

Open Meals is known for its experimental food projects, like the "sushi teleportation" concept, which has robotic arms serving up sushi in the form of 3D-printed cubes. This upcoming venture takes the idea of a futuristic sushi restaurant to new extremes.

Guests who plan on dining at Sushi Singularity will receive a health test kit in the mail, with vials for collecting biological materials like urine, saliva, and feces. After the kit is sent back to the sushi restaurant, the customer's genome and nutritional status will be analyzed and made into a "Health ID." Using that information, Sushi Singularity builds personalized sushi recipes, optimizing ingredients with the nutrients the guest needs most. The restaurant uses a machine to inject raw vitamins and minerals directly into the food.

To make things even more dystopian, all the sushi at Sushi Singularity will be produced by a 3D-printer with giant robotic arms. The menu items make the most of the technology; a cell-cultured tuna in a lattice structure, powdered uni hardened with a CO2 laser, and a highly detailed model of a Japanese castle made from flash-frozen squid are a few of the sushi concepts Open Meals has shared.

The company plans to launch Sushi Singularity in Tokyo some time in 2020. Theirs won't be the first sushi robots to roll out in Japan: The food delivery service Ride On Express debuted sushi delivery robots in the country in 2017.

[h/t designboom]

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