Sticks and stones may break your bones and words may hurt you. From name-calling to rumor mongering, bullying takes a lot of different forms. Thanks to social media, the Internet has become a prime locale for harassment. And for teens and adolescents (and the grown-ups they'll become), the result can be a lot worse than a few hours of tears or a lost friendship.

In fact, Dutch police recently arrested a man who may have been behind the online bullying that led 15-year-old Amanda Todd to commit suicide in 2012. And even though most people never experience the kind of brutal harassment Amanda Todd encountered, milder forms of bullying can still leave emotional scars that can mar your health and happiness (or even your professional success) for decades. [Tweet this!]

What Happens When You're Bullied

The simplest way to define bullying may be an "intrusion or violation of one's physical or psychological space." That comes from doctors at the U.S. Naval Observatory and research on post-traumatic stress disorder (PTSD), which can include bullying. Bullying can be "direct," meaning you're physically or verbally assaulted, or "indirect" (rumor spreading or being excluded), explains Dieter Wolke, Ph.D., a developmental psychologist at the University of Warwick in the U.K. Wolke says women are more often victims of indirect bullying, and are also more likely to be harassed using social media (because they tend use social sites more than men).

When you experience a threat-to your body or social standing-your brain releases the stress hormone cortisol, raising your blood pressure and heart rate, dilating your pupils, and priming your body to defend itself, the PTSD researchers say. Normally, that's no big deal. Your brain and body return to regular within a few minutes or hours. But if you experience severe bullying, your skittish brain gets "stuck" in a cortisol-fueled, high-alert status when it should be calm. Stated scientifically, pathways and neurons in your brain lose elasticity, or their ability to recover quickly from minor stressors-a form of permanent damage, researchers say.

A study from Rockefeller University found mice that were bullied developed a heightened reaction to the hormone vasopressin. Along with distorting your brain's ability to regulate responses to social situations, a haywire vasopressin response could lead to higher rates of depression and social phobias, their research suggests.

There are three major factors that determine how much bullying can permanently mess with your head: the duration of the torment, the severity of the torment, and your ability to escape it, Wolke says.

The Long-Term Consequences

Being bullied, especially if you were harassed as a child (when your developing brain is particularly vulnerable to trauma), can lead to lasting mental health problems including higher rates of anxiety, depression, and personality disorders, Wolke says. Even worse: Those psychological struggles can persist for 40 years or more. A recent King's College London study found 50-year-old adults who were bullied as kids suffered from suicidal thoughts and other psychological disorders at higher rates than folks who weren't bullied. Those who were bullied were also in poorer shape, performed worse on intelligence tests, struggled with higher rates of unemployment and lower pay, and were less likely to be in a romantic relationship. Bullying is roughly as damaging to a child as experiencing abuse or neglect, study authors say.

But how can it be so bad for you? Apart from the PTSD-style brain changes, there's also evidence that harassment during childhood can prematurely age your DNA. A Brown University report linked childhood trauma to shorter telomeres, the protein caps on the ends of your chromosomes that protect your DNA from wearing down. Chronic stress might cause this damage, which loads of research has tied to greater risks of diseases like heart disease, breast cancer, and diabetes.

There's not as much evidence linking adult bullying to all of these negative health and happiness consequences, but workplace bullying can have similar long-lasting setbacks, says Wolke. And many victims suffer in silence, which compounds the damage. "Talking to someone is a good first step," he says. "One first has to disclose."