Enduring psychobiological effects of childhood adversity
Introduction
Although a healthy psychobiological adaptation to severe stress or traumatization in terms of resilience can be observed in children and adults, many suffer from negative short- and long-term consequences. Maladjustment to childhood trauma is associated with psychopathological consequences of past victimization and physiological dysfunctions during both youth and adulthood. As is known from recent studies, trauma-related psychiatric disorders such as posttraumatic stress disorder (PTSD), depression (with suicidal ideation and suicide attempts), substance abuse, or somatoform disorders are often interconnected with physical diseases (Egede and Dismuke, 2012, Qureshi et al., 2009). Although such complex medical and psychiatric comorbidities are the most problematic consequences of traumatic experience, all forms of resulting (mal)-adjustment can be collocated on a continuum. At the one end, subjects who experienced severe stress or were traumatized show good mental and physical health with strong resilience or marginal psychobiological abnormalities, which can be subsumed under variations within the normal range. On the other end, severe comorbid psychiatric disorders, often in co-occurrence with physical complaints such as diabetes, obesity, stroke or heart diseases, are to be found and seem to persist even when life quality improves during later life (Kittleson et al., 2006).
To increase the knowledge about the complex psychobiological mechanisms of (mal)-adjustment to severe stress, recent research uses elaborate methodological approaches at a variety of psychobiological levels in diverse groups of traumatized subjects. Besides cross-sectional studies, an increasing number of studies draw on prospective and retrospective longitudinally assessed data of large community cohorts, or survey high-risk populations for severe stress or traumatization (Erni et al., 2012, Haller and Chassin, 2012). Logistic regressions indicate that a large amount of total variance explaining adolescent or adult psychiatric and physical maladjustment is predicted by early adverse life conditions including pre-, postnatal, or childhood exposure to highly stressful conditions.
The following description of recent research on the psychobiological sequelae of adverse living conditions and trauma during childhood refers to a clear selection of seminal topics of the entire research field. First, the terms childhood trauma and childhood adverse living conditions will be defined in order to clarify whether the adverse conditions result from stress or trauma. It needs to be established whether recent data can be used to confirm or disprove the assumption that traumatic experiences may have more severe or different psychobiological consequences than chronic stress. Second, the interplay of adverse living conditions, lifestyle factors such as unhealthy diet and low physical activity, or genetic dispositions will be demonstrated for selected stress systems such as the hypothalamus–pituitary–adrenal (HPA) axis and its related hormones. As a consequence of methodological advances, recent research indicates the control of the sympathetic nervous system and HPA axis via the immune system (IS) (Chrousos, 2009, Glaser and Kiecolt-Glaser, 2005). This review focuses primarily on the HPA axis and the immune system for two reasons: First, most of the psychobiological studies assessing stress and trauma in childhood refer to the HPA axis. Stress research has been extended to genetic dispositions and epigenetic processes influencing the HPA axis, which may help to explain the diversity of adaptive processes to negative life conditions. Second, since maladjustment may result not only in psychiatric disorders but also in physical disease such as obesity, coronary heart disease or diabetes, it appears to be necessary to elucidate the effects of severe or chronic stress on immune processes, which in turn seem to influence physiological stress systems. These interactive processes and their psychopathological consequences for individual developmental processes will be discussed with respect to PTSD as the most prominent disorder associated with childhood adversity. Finally, some light will be shed on the question of whether child development research provides evidence of specific phases of increased risk onset of pathological processes due to adverse living conditions during these life phases.
Section snippets
Maltreatment during childhood
Childhood adversity and trauma rarely occur as a single event but seems to consist of continued maltreatment involving one or more malicious acts. At least five major forms of maltreatment during childhood can be classified: physical abuse, physical neglect, sexual abuse, emotional abuse, and emotional neglect (Torchalla et al., 2012). Besides the co-occurrence of at least two types of ongoing primary traumatic experiences such as early physical neglect, maternal emotional unavailability, or
Hypothalamus–pituitary–adrenal (HPA) axis dysregulation
It is well known that the HPA axis reflects stress reactivity. Under healthy conditions, various forms of physiological and psychological stressors provoke an increase in the production and secretion of corticotropin-releasing hormone (CRH), which is released from the paraventricular nucleus of the hypothalamus into the portal circulation. This stimulates the anterior pituitary gland to release adrenocorticotropic hormone (ACTH). ACTH activates the adrenal gland to release cortisol. This
Are sensitive child developmental periods related to the severity of negative trauma consequences in later life?
Published prospective studies on childhood adversity and its impact on later life describe different ages of trauma onset and a variety of outcome measures assessed at different times during later life. The published results of these studies do not allow conclusive statements about whether the developmental age at trauma onset influences the type of sequelae manifested by the maltreated children. Nevertheless, recent findings from neuroendocrinology and developmental neuroscience support the
Conclusions
There has been a formidable increase in knowledge about the interconnectivity between genetic dispositions, epigenetic mechanisms, stress-related hormonal systems and immune parameters to describe short-term and long-lasting consequences of childhood traumatization. Unfavorable constellations between these systems, such as low cortisol levels and elevated markers of inflammation in victims of adverse childhood conditions, may promote the co-occurrence of physical and psychiatric pathologies.
Conflict of interest statement
None declared.
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