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“Exercise is a form of stress,” she pointed out. So is social isolation. Each, independently, induces the release of stress hormones (primarily corticosterone in rodents and cortisol in people). These hormones have been found, in multiple studies, to reduce neurogenesis. Except after exercise; then, despite increased levels of the hormones, neurogenesis booms. It’s possible, Dr. Stranahan said, that social connections provide a physiological buffer, a calming, that helps neurogenesis to proceed despite the stressful nature of exercise. Social isolation removes that protection and simultaneously pumps more stress hormones into the system, blunting exercise’s positive effects on brainpower.

Most plastic products, from sippy cups to food wraps, can release chemicals that act like the sex hormone estrogen, according to a study in Environmental Health Perspectives. The study found these chemicals even in products that didn't contain BPA, a compound in certain plastics that's been widely criticized because it mimics estrogen.

The testing showed that more than 70 percent of the products released chemicals that acted like estrogen. And that was before they exposed the stuff to real-world conditions: simulated sunlight, dishwashing and microwaving, Bittner says.

Early reaction to the study was mixed. Some scientists wondered about the test's reliability. Others noted that wine and many vegetables also can act like estrogen. And a few observed that Bittner has a financial interest in the testing lab and in a company involved in making plastic products that don't release estrogenic chemicals.

Casually flipping through a 2006 copy of the Annals of the New York Academy of Sciences, I learned that exercise is the key to combating the stress of modern life.The authors, from the University of Ioannina in Greece, first explain (in regards to the fight-or-flight response) that "stress responses can be elicited by emotional stimuli or professional and social stress."

It takes just one negatively worded memo handed down from on high to get the glucocorticoids and catecholamines flowing, but these adrenal hormones go unused and are stored in visceral fat deposits, and this does bad things to you.

these stored adrenal hormones disturb gonadal function (no wonder Viagra is such a big seller), as well as growth hormone and thyroid function. They explain how these "metabolic disturbances" lead to "comorbidities including central obesity, hypertension, dyslipidemia, and endothelial dysfunction." In other words, unrelieved stress turns you into an artery-clogged hippopotamus with Limbaugh-like blood pressure and a lousy immune system. Oh, and it's also hard on your brain.

A growing body of research shows that working out with weights has health benefits beyond simply bulking up one's muscles and strengthening bones. Studies are finding that more lean muscle mass may allow kidney dialysis patients to live longer, give older people better cognitive function, reduce depression, boost good cholesterol, lessen the swelling and discomfort of lymphedema after breast cancer and help lower the risk of diabetes. "Muscle is our largest metabolically active organ, and that's the backdrop that people usually forget," said Kent Adams, director of the exercise physiology lab at Cal State Monterey Bay. Strengthening the muscles "has a ripple effect throughout the body on things like metabolic syndrome and obesity."

Strength training often takes a back seat to cardiovascular training, but it can benefit the heart in ways that its more popular cousin can't. During cardio exercise, the heart loads up with blood and pumps it out to the rest of the body: As a result, Potteiger said, "the heart gets better and more efficient at pumping." But during resistance training, muscles generate more force than they do during endurance exercises, and the heart is no exception, Potteiger said. During a strength workout, the heart's muscle tissue contracts forcefully to push the blood out. Like all muscles, stress causes small tears in the muscle fibers. When the body repairs those tears, muscles grow. The result is a stronger heart, not just one that's more efficient at pumping. Another big advantage of working out with weights is improving glucose metabolism, which can reduce the risk of diabetes. Strength training boosts the number of proteins that take glucose out of the blood and transport it into the skeletal muscle, giving the muscles more energy and lowering overall blood-glucose levels. "If you have uncontrolled glucose levels," Potteiger said, "that can lead to kidney damage, damage to the circulatory system and loss of eyesight."

The brain may get a boost from the body's extra muscle as well. A 2010 study in Archives of Internal Medicine found that women ages 65 to 75 who did resistance training sessions once or twice a week over the course of a year improved their cognitive performance, while those who focused on balance and tone training declined slightly. One reason for the improvement, researchers believe, may be that strength training triggers the production of a protein beneficial for brain growth.

Children of depressed parents are two to three times as likely to have major depression. Maternal depression in particular has been shown to have serious effects on development, primarily through an absence of responsiveness — the parent’s conscious and consistent mirroring and reciprocity of an infant’s gaze, babble and actions. “Depressed mothers often respond to their babies from the beginning in ways that dampen their enthusiasm and joy,” says Alicia Lieberman, a professor in the department of psychiatry at the University of California, San Francisco. This is problematic, as 10 to 20 percent of mothers go through depression at some point, and 1 in 11 infants experiences his mother’s depression in the first year.

Many researchers, particularly those with medical training, are eager to identify some kind of a “biologic marker” to make diagnosis scientifically conclusive. Recent studies have looked at the activity of cortisol, a hormone the body produces in response to stress. In preschoolers who have had a diagnosis of depression, as in depressed adults, cortisol levels escalate under stressful circumstances and then fail to recover with the same buoyancy as in typical children.

But in adults, cortisol reactivity can be an indication of anxiety. Other research has found that in young children, anxiety and depression are likewise intertwined. At Duke, Egger found that children who were depressed as preschoolers were more than four times as likely to have an anxiety disorder at school age. “Are these two distinct but strongly related syndromes?” asks Daniel Pine of the N.I.M.H. “Are they just slightly different-appearing clinical manifestations of the same underlying problem? Do the relationships vary at different ages? There are no definitive answers.”

People with a history of heart disease who are prone to negative thinking, gloom, and inhibition -- a personality profile known as Type D (for "distressed") -- are nearly four times more likely to experience heart attack, heart failure, heart rhythm disorders, death, and other negative outcomes compared to heart patients with a different personality profile, the study found.

"There is a clear connection between heart risk and psychological risk factors, and those people who have this personality and lack social support have higher risk of health problems,"

Type D personalities are "characterized by negative emotions like anxiety, frustration, and anger, and at the same time score high on social inhibition, meaning that they are less likely to disclose emotions," Denollet says.

According to the American Psychological Association, a whopping 75 percent of people in the United States feel stressed out. Almost half of us eat unhealthy because of it; 47 percent of us can't sleep because of it; it makes one in three of us depressed; and for 42 percent of us, it has gotten worse in the last year. There is so much making us anxious these days -- from big-picture problems like uncontrollable oil spills and a still-soft economy to garden-variety job, relationship, money, you-name-it woes -- that it's easy to think of chronic stress as the new normal.

the latest research reveals that revving up your body with exercise may be the most effective antidote. In lab studies, when scientists at Princeton put animals on a six-week aerobic conditioning program, then compared their brain cells with those of a group that remained sedentary, they found that the "brains on exercise" morphed over time into a biochemically calm state that remained steady even when the subjects were under stress. The nonexercising group's brain cells continued to react strongly to anxiety-inducing situations. This breakthrough discovery has scientists now saying that cardio workouts may actually remodel the brain to make it more resistant to stress hormones.

Researchers at Oregon Health and Science University scanned the brains of nine healthy, normal-weight  subjects in the minutes after each got an infusion of equal volumes of glucose, of fructose and of saline. The brain scans aimed to capture activity in a relatively small swath of the human brain in and around the hypothalamus, which plays a key but complex role in setting appetite levels and directing production of metabolic hormones. The researchers, led by Dr. John Purnell, found that "cortical control areas"--broad swaths of gray matter that surrounded the hypothalamus -- responded quite differently to the infusion of fructose than they did to glucose. Across the limited regions of the brain they scanned, Purnell and his colleagues saw that glucose significantly raised the level of neural activity for about 20 minutes following the infusion. Fructose had the opposite effect, causing activity in the same areas to drop and stay low for 20 minutes after the infusion. Saline--the control condition in this trial--had no effect either way.