Childhood trauma and the brain – Part One

In my book I identify that one of the most important and influential risk factors that renders people vulnerable to addiction is childhood trauma.  How and why this changes a child’s developing brain is still largely a mystery, but several lines of research show that these changes occur. This entry will be a two part exploration of the effects of childhood trauma.

For example, in my book I describe a fascinating, yet quite simple, study reported by a research group in Exeter in England.  They interviewed a number of non-drug using adults and divided them into a group who had reported experiencing childhood trauma, and a group who hadn’t.

They then induced these participants to receive a dose of morphine. They were interested in measuring how these participants reacted to the dose. In general, the non-trauma group found the experience to be very intense, almost too powerful, somewhat aversive, and they didn’t want to receive another dose. In contrast, the trauma group reported much more positive feelings. Some found the dose pleasurable and even would be willing to receive another dose.

Clearly something had changed in the brains of the participants who had experienced childhood trauma. What is also interesting is that the type of trauma didn’t seem to matter. In this article, I will describe some research that sheds some light on these changes, although we still know relatively little about the underlying mechanisms that produce them.

To begin with, there was some fascinating research reported by McGill neuroscience professor, Michael Meaney, in the late 1990s. Meaney produced mild stress in infant mice by removing them from their mother for 15 minutes a day, during their early life. By measuring various indicators, he then discovered that these mice were much better at controlling their stress response in their later adult life.

These mice regained their heart rate equilibrium and reduced their blood levels of cortisol (actually corticosterone, the rodent stress hormone) back to normal values. Follow-up research discovered that the triggering mechanism for these changes was that the mother would vigorously lick the mouse pup when it was returned to her. Somehow this activated the brain changes manifested in later life.

This led to further research where graduate students stimulated mice in a similar way by stroking their backs with small paintbrushes. These treatments produced similar improvements in the capacity to deal with stress as adults. Since then, more has been discovered about the developmental pathways in the brain that underlie these changes. Clearly, seemingly mild early experiences can produce profound changes in the developing brain.

If we consider the nature of the stresses, or trauma, that can activate these, and other, changes, the first question that arises is what kinds of experiences constitute stress for the developing child? The natural answer to this question is obviously those situations that we, as adults, conceptualize as traumatic. For example, we would immediately identify physical or sexual trauma, or neglect, as fitting this list.

However, many of us would also identify a lack of adequate attachment as traumatic. On the other hand, what about the child growing up in a wealthy household, but one that is wealthy because both parents are working long hours? The lack of so-called quality time with the parents can have equally problematic results, according to individuals who reported these experiences.

A review from UC Irvine in California of many studies focusing on childhood trauma and addiction has revealed an additional type of trauma that most adults would never consider initially. The immature brain turns out to be susceptible to unpredictability with respect to the kinds of sensory experiences that will occur in the child’s environment, even if they are not specifically aversive. A lack of security in knowing when events will occur, such as feeding or cuddling or just enjoyable interaction can be stressful. If this is coupled with aversive events, the effect can be even more powerful.

In hindsight, this should not be all that surprising. We have known for a long time that how stressful a situation is depends on three main factors. First, the intensity of the event, second, whether there can be any control over the event, which leads to the third powerful factor, unpredictability. While each of these factors contributes to the intensity of the stress felt, all three combined can produce very intense stress responses.

Currently, research on these effects is proceeding on a number of levels.  In Part Two of this entry, I’ll identify some of the studies and what they are revealing.