In the mid-1980s, a doctor named Vincent Felitti was running Kaiser Permanente's Department of Preventive Medicine in San Diego. One of the programs offered was an obesity clinic, and the program should have been a resounding success. But Felitti was mystified by the high attrition rate: over 50% of the participants in the obesity clinic dropped out before meeting their weight-loss goals. (The clinic worked with folks who wanted to lose as little as 30 lbs, although it was really designed more for those who wanted to lose 100 lbs or more.) The really weird thing was this, though: the dropouts left the program even though they were losing weight.

Felitti wondered, as time went on, if weight gain might actually be a coping mechanism—could weight gain be a way of lessening the pain of childhood trauma and specifically, childhood sexual abuse? Eventually Felitti and a colleague, Dr. Robert Anda of the Centers for Disease Control, surveyed nearly 20,000 patients for various forms of childhood trauma, and the results were an eye-opener: childhood emotional trauma and stress were found to be strongly correlated with everything from high-risk behaviors in adult life (like sexual promiscuity and alcohol abuse) to a greater risk of heart disease, cancer, and chronic lung disease.

The test they administered is now known as the Adverse Childhood Experiences test, or ACE test. It's a simple-to-take but powerful diagnostic tool that generates a 0-10 score, which can offer significant insights into your risk for a number of high-risk behaviors, including addiction—as well as your risk for other serious physical and mental illnesses.

The idea that childhood trauma might have a connection with adult health problems came to Felitti almost by accident, according to a recent interview. He was running through a series of questions when he accidentally asked a client in the weight-loss program, "How much did you weigh when you first became sexually active?" instead of "How old were you when you were first sexually active?" The patient said, "Forty pounds," and went on to reveal, through tears, that it had been with her father. Felitti says, "I remember thinking, 'This is only the second incest case I've heard about in 23 years of practice.'"

As time went by, and Felitti began probing the subject more deeply, he realized that many of his clients had suffered sexual abuse and other traumas—both in childhood and in adulthood. At first, fellow professionals didn't want to believe what he was telling them—in part, it was possible to deny the validity of his findings thanks to the small number of people he'd interviewed. (Medical studies, to be statistically valid, need to include a reasonably significant number of people.) But Felitti found an interested ear in Dr. Robert Anda, an epidemiologist at the Centers for Disease Control.

Felitti remembered, vividly, a remark a sexual abuse victim had made during an interview: "Overweight is overlooked, and that's the way I need to be."

The discussions between Felitti and Dr. Anda were to eventually lead to a much larger-scale study, in which over 17,000 individuals—all members of the Kaiser HMO—reported on the number of traumatic childhood experiences that they'd been through. As you might imagine, the study was a long one and took place over the course of a decade or so. What became known as the ACE Study, determined that seven basic categories of “adverse childhood experiences”:

psychological, physical, or sexual abuse;

violence against one’s mother;

living with household members who were substance abusers, mentally ill, suicidal, or imprisoned

were risk factors for behaviors like alcohol abuse, substance abuse in general, high-risk behaviors, and other health problems.

The test in its current form consists of 10 questions that evaluate these seven factors, as well as the absence of an emotionally supportive environment, physical neglect, and loss of a parent due to divorce or abandonment; a yes answer to any of these questions is counted as one point on the 1-10 scale. For instance, on this scale, persons with an ACE score of four or more were twice as likely to be smokers, 12 times more likely to have attempted suicide, seven times more likely to be alcoholic, and 10 times more likely to have used intravenous street drugs. As time went by, and data accumulated, it became clear that traumatic childhood experiences weren't just correlated with high-risk behaviors, but with other medical problems as well.

A 1998 study published by Felitti and Anda in the American Journal of Preventive Medicine details some of the correlations that the two physicians uncovered. Felitti and Anda evaluated seven categories of "adverse childhood experiences" and discovered that among the nearly 10,000 respondents at the time the study was published, "more than half of respondents reported at least one, and one-fourth reported more than two, categories of childhood exposures" (to traumatic experiences).

Here's the kicker: Felitti and Anda wrote that, "persons who had experienced four or more categories of childhood exposure, compared to those who had experienced none, (in addition to the connection between high ACE scores and high-risk behaviors noted above) had a greater risk of a whole host of stress-related physical ailments. They wrote that they had discovered "a graded relationship to the presence of adult diseases including ischemic heart disease (basically, risk of heart attack) cancer, chronic lung disease, skeletal fractures, and liver disease. The seven categories of adverse childhood experiences were strongly interrelated and persons with multiple categories of childhood exposure were likely to have multiple health risk factors later in life."

To understand just how high levels of stress can create negative impacts in childhood that resonate well into adult life, it's important to understand that the brain isn't fully developed at birth. Rather, the brain continues to develop in significant ways throughout childhood, adolescence, and early adulthood. We sense this intuitively (many parents of teenagers wonder how their child's personality could have changed so abruptly!) but high levels of stress throughout these phases of life can have negative impacts down the road.

Harvard University's Center on the Developing Child recognizes three basic types of stress, and three basic types of stress response.

1. The first is the so-called positive stress response—in a nutshell, you might say this is normal, everyday stress that primes the nervous system, and the body in general, to cope with the sometimes significant stressors that a child will encounter in later life. You can think of these as exercises, in a way, that leave the mind and body better prepared to deal with what a person will eventually have to deal with in adulthood (the Center mentions such things as receiving a new caregiver, or getting immunized.)

2. The next level are so-called tolerable stress responses. Here, things are a little more dicey—the tolerable stress response is a response to genuinely traumatic events, like losing a loved one, a bad injury, or a natural disaster. These could be devastating events—but what makes them tolerable, and even an aid to having greatly improved coping skills in adulthood, is whether or not the child going through them has a supportive environment, and especially, supportive adults. If the answer is yes, then the result might well be better coping skills down the road; if the answer is no, then the outcome might not be so rosy.

3. The most negative stress response is the "toxic stress response." You get a toxic stress response when there are powerful negative events that take place in the absence of adult support, and/or when such events take place often over time. These are the real horrors of childhood: the feeling of being helpless, combined with ongoing "emotional abuse, chronic neglect, caregiver substance abuse or mental illness, exposure to violence, and/or the accumulated burdens of family financial hardship—without adequate adult support."

This third case is potentially the most hazardous. We now know that when under any kind of stress, the body releases substances known as hormones that alter body function; stress hormones can be very helpful over the short term, but over the long term they can cause significant harm. Most importantly, stress hormones over an extended time period can actually cause physical changes in the developing brain—leaving a person more vulnerable to both high-risk behaviors like addiction, and to serious physical illnesses (and, of course, the two often go hand-in-hand.)

Now, it's possible to take the ACE test online and if you do, you might find yourself wondering just how seriously you should take the results—are you really doomed to a lifetime of high-risk behaviors, and to a high risk of serious illness, thanks to events over which you had no control as a child? Jack Shonkoff, at the Center for the Developing Child at Harvard University, points out that while the ACE test can be a powerful, predictive and diagnostic tool, it also often fails to identify mitigating factors that might significantly reduce your chances of hurting in adult life because you were hurt as a child.

In a 2015 NPR article, journalist Laura Starecheski noted that the ACE score is "not a crystal ball," and in the same article, Shonkoff remarked, "There are people with high ACE scores who do remarkably well." How's this possible? Well, the problem with the ACE test is that it only asks about the bad, and totally ignores the good. The good things that can happen in childhood—and which help, potentially, counteract the bad—are known as "mitigating experiences." While the ACE score is a pretty good guideline as to what major red flags in a person's childhood might be, it's not a certain indicator of what adult life might be by any means. And, as well, it’s important to remember that if you are a parent who’s struggled with issues like substance abuse and addiction, or who’s been with your child through a divorce, that these mitigating experiences can considerably counteract the negative effects evaluated by the ACE test.

The results are fascinating, if not crude. The ACE quiz asks about experiences under the age of 18 but a child who experiences divorce at age five has a very different experience than the child whose parents divorce at age 16 or 17.

There is as much missing as there is there. For example, "positive" or "restorative" childhood experiences are not included in the study. Those types of experiences can actually add to the ever-important quality of resiliency. For example: Did the child with the incarcerated parent have a loving grandparent who cared for him/her? Was there a teacher who took special interest in the child of the drug-abusing parent and made the child feel special, smart, appreciated? Did the alcoholic/drug addicted parent(s) ever become sober, thus teaching the child that the ability to heal and change is real and possible? The ACE quiz cannot in 10 yes or no questions gather that information.

The insights gained by Felitti and Anda are powerful, and a clear warning to be aware of the risks posed by childhood physical and emotional trauma—and the risks posed to the developing brain by such events. But like any single test, it doesn't capture the whole person—and it's in just those aspects of life that hope lies for transcending even the most traumatic childhood experiences.