A Girl’s Brain Is a Vulnerable Brain—in Unique Ways
Ten percent of men with an ACE Score of 1 suffer from chronic depression; 18
percent of women do. Likewise, 33 percent of men with an ACE Score of 4 or
more later develop depression—already a high, disturbing figure—while nearly
60 percent of women with that score develop chronic depression in adulthood.
The risk that toxic stress will lead to neuroinflammatory diseases such as
depression and anxiety disorders is, as with autoimmune disease, nearly twice as
high for women as it is for men.
At the University of Wisconsin, neuropsychiatrist Ryan Herringa, MD, PhD,
and assistant professor of child and adolescent psychiatry, recently asked a fairly
typical group of sixty-four eighteen-year-olds—who were being followed by
Herringa’s colleagues in a longitudinal study known as the Wisconsin Study of
Families and Work—to answer questions about the adversity they’d faced.
They were asked to agree or disagree with statements such as “when I was
growing up people called me things like ‘stupid,’ ‘lazy’ ”; or, “people in my
family said hurtful or insulting things to me”; or, “I thought my parents wished I
had never been born”; or, “I felt that someone in my family hated me,” as well as
questions about more overt physical and sexual abuse and emotional neglect.
Then Herringa had the teens undergo MRI brain imaging, in order to measure
the connections between three areas of the brain that process and overcome fear.
One of these areas, the prefrontal cortex, helps to analyze thoughts, reflect on
them, and decide how to act and behave. You might think of the prefrontal
cortex as something like an experience simulator. We try things out in our heads
before we actually do them in real life. We can also decide how we feel about a
person or place or event that took place in our past, or how we feel about
something that’s about to happen, like an upcoming lunch with an old boyfriend.
The prefrontal cortex takes its cue on how to process thoughts and reflections
from the amygdala, the brain’s fear and emotion center—which triggers the
fight-or-flight reaction whenever we feel threatened or afraid, or when we
remember being in dangerous situations.
The third area of the brain is the hippocampus, which stores memories and
helps distinguish false alarms from the real danger signals that the amygdala
sends.
As Herringa explains, “If you’re at home watching a scary movie at night, the
hippocampus can tell the prefrontal cortex that you’re at home, this is just a
movie, and there is no reason to go into full fight-or-flight response or freak
out.”
At least that’s how these three areas of the brain work together if the brain
circuitry that connects them is working correctly. And researchers can see how
strong the working connection is through MRI imaging.
Herringa discovered that there was a dramatic difference in the connection
between the prefrontal cortex and the hippocampus in both male and female
teens who’d suffered adversity, compared with teens who had faced none.
To some degree, that was expected, but these brain changes had occurred even
in kids who were experiencing very common,
much milder
forms of childhood
adversity in the home, including name calling, teasing, parents who reacted
harshly to them, or lack of emotional nurturance.
As a result, “the hippocampus may be having trouble feeding the correct
information to the prefrontal cortex about when and where to feel safe, and when
not to feel safe, in daily life.” This was true even for teenagers who were
not
considered abused, but who had more difficulty differentiating between safe and
unsafe environments. This could lead, in turn, to a state of “hypervigilance, of
constantly looking around the next corner for the next emotional or physical
threat.”
Herringa’s study provides hard, physical evidence that even mild, low-grade
adversity, when chronic, leads to a revved-up alarm system and to inflammation.
For parents, this study’s findings may seem worrisome, but we’re not talking
about the occasional moment when parents are irritated with their kids at the end
of a long, stressful workweek or frustrated when the kids won’t turn off their
computer game to take out the trash. Many parents have had less-than-mindful
moments and later regretted being too harsh with a child they love and would
never consciously harm. This may be especially true for parents who are already
overwhelmed, dealing with health issues, financial stressors, or other problems
that are taxing their resources. Or, if they received very little nurturance when
they were kids, they may lack the parenting skills to do better with their own
kids than their own parents did with them. Often, says Herringa, “this is about
parents trying to deal with the harsh events in their own lives, and they don’t
mean to take it out on their children. They are good parents, doing the best they
can with what little they have.”
This is not about blame.
But we can use this knowledge about the effect of repeated stress on children
we treasure in order to become more mindful parents, coaches, and mentors.
(We’ll address that directly in Chapter Eight.)
Another surprising finding in Herringa’s research was that bad experiences were
tied to weaker neural connections between the prefrontal cortex and the
hippocampus in the brains of both teenage girls and boys. But neural
connections in girls were
also
weaker between the prefrontal cortex and the
amygdala, the fear center of the brain itself.
What did this mean? According to Herringa, “This connection between the
prefrontal cortex and the amygdala is a direct connection that helps to control
our fear and emotional responses.” It plays an essential role in determining how
emotionally reactive we’re likely to be to the things that happen to us in our day-
to-day world—and how likely we are to perceive events as stressful or
dangerous.
“If you are a girl who has had Adverse Childhood Experiences and these brain
connections are weaker, you might expect that in just about any stressful
situation you encounter as life goes on—financial stress, a near accident while
driving, relationship stress, or family arguments—you may experience a greater
level of fear and anxiety in those situations,” says Herringa.
Girls with these weakened neural connections are more likely to develop
anxiety and depression by the time they reached late adolescence. This
correlated with Herringa’s observations of young women he’d been following in
his clinic for some years. These girls “seemed to be afraid everywhere. It’s like
they’ve lost the ability to put a contextual limit on when they’re going to be
afraid and when they’re not.” They suffered from fear and anxiety that other
teenagers their age who hadn’t met with adversity simply were not experiencing.
According to Herringa, maltreatment in childhood impairs the regulatory
capacity of the brain’s fear circuitry. Moreover, maltreatment’s effect on girls’
frontal lobe, amygdala, and hippocampal connectivity “may help explain
females’ higher risk for later having anxiety and depression.”
Meanwhile, other researchers have been looking at childhood adversity’s effect
on the brain through other lenses. Hilary P. Blumberg, MD, professor of
psychiatry and director of the Mood Disorders Research Program at Yale School
of Medicine, studied forty-two adolescent boys and girls, ages twelve to
seventeen, who’d been through childhood trauma and found that there were
differences in which areas of the brain were affected depending on the type of
adversity they had encountered.
For instance, those who’d experienced physical abuse showed decreases in the
prefrontal cortex, as well as in an area of the brain known as the insula cortex.
“The insula is associated with having a sense of bodily ownership and personal
agency,” says Blumberg. These findings suggest that “decreases in this area
might be associated with the feelings of disassociation that children who’ve
experienced physical abuse so often report.” Kids disassociate from the sense
that they are in their own bodies because it’s the only way they can escape the
terror of what’s happening to them. They simply “go elsewhere” mentally—as if
it isn’t their arm being twisted, or face being slapped, or body being sexually
assaulted.
Those children who’d been neglected emotionally showed decreases in areas
of the brain that are associated with emotional regulation. Emotional
maltreatment, Blumberg says, may “alter the development of the brain circuitry
that regulates emotions—in ways that make adolescents more prone to
depression.”
Blumberg also found striking overall differences in where specific brain
changes occurred based on whether a child was male or female. Girls who
reported adversity were more likely to experience decreases in gray matter
volume in brain regions associated with regulating emotions, and depression—
including the prefrontal cortex, amygdala, and hippocampus.
Boys, on the other hand, were more likely to show decreases in brain matter
volume in the caudate region of the brain—an area responsible for impulse
control and behavior.
Blumberg speculates that the difference in brain changes that occur in girls
and boys “might contribute to the relatively greater risk for mood disorders in
girls, and disorders of impulse control in boys” who have been exposed to
childhood adversity.
Certainly girls can have issues with attention and impulse control, and boys
can become depressed and anxious in the aftermath of adversity. Any child
psychiatrist can attest to that. Moreover, kids who have never been treated
harshly can develop depression, anxiety, and ADHD. Diet, genetics, chemicals,
viruses, and infections all play a part. But this recent understanding of the impact
of adversity on the brain, and the differences between boys and girls, can help
explain some of the adolescent suffering we see.
Ten-year-old Laura’s mom faces the loss of her marriage, is depressed and
anxious, and criticizes and puts down her daughter regularly. Seven-year-old
Stephen’s dad is under extreme work and financial pressures, and he screams at
his son over a flip-flop lost in a lake and calls him “pretty boy.” This stress
prunes away neurons in the young, developing brain.
Laura and Stephen seem just fine for years; they show no signs of what’s
happening in their own homes. They smile, do well in school. As they grow into
their teen years, however, and their brains go through the normal, developmental
pruning process, and neurons are lost, suddenly their brains are functioning at a
suboptimal level, shy of the connections needed to create the kind of well-
functioning, integrated circuitry to manage mood, suss out danger, and thrive.
Situations that should be everyday moments of complex, messy, but
manageable life become hurdles too high. Laura is anxious, reactive, fearful; she
has trouble gauging how to properly respond to disagreements small and large.
The stressful moments in her day-to-day life blur together; she is always
managing a low-grade buzz of anxiety.
As for Stephen, the neural connections between his hippocampus and the
prefrontal cortex may be weakened so that he’s less able to mentally weigh
whether something might be a good decision or not. He may appear indecisive,
disorganized. There may be changes, too, in the caudate area of his brain, so that
he’s less able to control impulsive behavior.
Indeed, research in animal models further illustrates these findings. When
researchers induced low states of inflammation into rats’ brains in the
hippocampus, the animals were no longer able to discern between safe and
nonsafe environments. Neuroinflammation disrupted specific neural circuits,
leading to impairment in decision making, making it harder to distinguish what
was good and what was bad and to make sound choices.
It’s a painful way to be in the world.
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