Since at least the time of Moses, we’ve wanted to believe that the “child is father to the man,” that to understand adults we need first look to their childhoods. In mental health care, this age-old folk notion takes the form of belief that your problems are all about your momma, or someone else who “bent the twig” and “shaped the tree.” Got problems? Look to your childhood.
In mental health care—and in psychology generally—the idea hasn’t fared so well in recent decades. The inaccuracy of childhood memories, the difficulty of scientists in finding robust correlations between early childhood and adult life, the rise of genetics in explaining such consistencies as turn up—these and other considerations have put the idea in ill repute.
Of late, mental health professionals still wedded to the idea have taken heart from the “ACE” research—adverse childhood events. People who suffer the distress we call mental illness have also suffered adverse childhood experiences at a far higher rate than “healthy” souls. Vindication of our beliefs! Right?
We need to be careful to read this research accurately, and to understand what it does and does not say.
While studies of Adverse Childhood Experience (ACE) differ a bit, generally they indicate that such experiences occur roughly three times more often in the lives of people who suffer schizophrenia, affective psychosis, depression, and personality disorders than they do in healthy souls, and a bit more often than that to people who suffer PTSD or dissociative disorders. (Anxiety disorders seem to correlate with ACE less often.) Obviously, then, ACEs increase the risk of mental illness.
But that’s all they do—increase the risk. They don’t cause mental illness, in any straightforward sense of “cause.”
To understand the significance of the ACE literature, we must look at the numbers more carefully. About six percent of adults in America suffer some sort of severe mental illness in any given year. That means that out of 1000 American adults, 60 suffer serious mental illness.
Depending on the study you read, we can assume that roughly half of those suffered ACE—most studies that I know say the rate is less than that, but let’s keep things simple for the sake of clarity. That means that out of 1000 American adults, 30 suffered ACE and developed a severe mental illness.
But 940 of those 1000 adults do not suffer a serious mental illness. If they have suffered ACEs only one-third as often (that is, if ACEs are three times more likely to happen to persons who suffer mental illness), that means about 17% of them suffered ACEs. That’s about 160 people.
So totaling the 30 mentally ill people who suffered ACEs and the 160 healthy people who suffered ACEs, we see that 190 people suffered ACEs.
The overwhelming majority of people who suffer ACEs do not develop mental illness. Obviously, it is too simple, and mistaken, to say that ACEs cause mental illness.
And mental illness can happen without any reported ACE. Perhaps the best meta-analysis of ACE and schizophrenia, for example, shows that if all ACEs were eliminated, psychosis would most likely only be reduced by about one-third.
The ACE research also does not show that genes aren’t implicated in mental illness. From behavioral genetics, we have reasonably good, well-evidenced knowledge of the heritability quotients of a great many mental disorders and other psychological characteristics. Schizophrenia and bipolar I—classic manic depression—are about 80% heritable. Major depression is much lower—about 40%. Panic disorder is a bit less heritable than that. Most psychological traits are heritable in the same range as depression and panic—30-40%. ACE research does not address, and does not contradict, that research.
Moreover, we do not know the extent to which ACEs themselves are due to genetic factors, so we cannot simply ascribe a particular level of significance to them. Most likely, they are less significant than the percentages suggest, because the correlation between ACEs and mental illness may be confounded, to some extent, by genetic factors. That is, the genetic factors that raise the probability of mental illness may themselves contribute to the occurrence of the ACEs.
A child and his or her father, for instance, may share whatever genetic material predisposes to major depression. The father may subject the child to neglect, abuse, or other harsh treatment because of traits associated with that genotype.
Or a child may be bullied because he or she shows early oddities due to the genetic predisposition.
Or the parents or children may suffer excessive risk-taking, or poor foresight, or impaired social perceptiveness, due to genetic factors, and these may result in conditions (e.g., poverty, instability) that promote ACEs.
In none of these cases could we say, then, to what extent the ACEs occur independently of the genetic predisposition that contributes to the mental illness.
We do not yet know how often genetic confounding occurs, or the extent of the effects. Research on confounding factors is only getting started; some early research claims to find no confounds. That’s a bit incredible, since we know that genetic factors mediate such things as a family’s socio-economic status, or parents’ tendencies to bad behavior, and other things which must surely sometimes contribute to ACEs. But we will have to see how this research develops over time.
We know, then, that ACEs increase the risk of developing mental illness, but we do not know just how much. We know that by themselves, ACEs cannot simply be said to cause mental illness. And we know that mental illness can occur in the absence of ACEs.
The distress that, rightly or wrongly, we call mental illness is real and terrible. Genetic factors contribute to it—and adverse childhood experience can, for some people, pose destructive challenges.
Neither genetics nor early childhood is the whole story, and the whole story will doubtless involve a great many other things—the progress and outcome of the story is assuredly not set, for most people, by one’s fifth or sixth or seventh birthday. In mental health care, we can continue to puzzle out the significance of childhood experience for mental distress. But the best research makes clear that we can’t rest content in easy, old superstitions about the power of the early years.