Reviews of Note

In an occasional column, Journal Watch Psychiatry editors briefly comment on review articles. These annotations were written by Barbara Geller, MD, Jonathan Silver, MD, and Joel Yager, MD.

What we know about TBI today. The April 2013 issue of the open-access journal Nature Reviews Neurology has a special focus on traumatic brain injury (TBI), with excellent articles by top researchers reviewing the current state of knowledge in TBI.1 They discuss changes in the epidemiology of TBI (the mean age is increasing), sports-related TBI, the relationship between repetitive TBI and dementia, chronic traumatic encephalopathy, the usefulness of intracranial monitoring, and potential biomarkers in mild TBI (blood and cerebrospinal fluid). These balanced and critical reviews are an important resource.

Why does anorexia nervosa persist? Starting with the observation of the commonly persistent course of anorexia nervosa, this renowned authority suggests that in addition to understanding biological and social vulnerabilities and reinforcers, we should see eating disorder–related behaviors as habits.2 The habits become fixed through sheer repetition, are reinforced by helping patients cope with negative affect, and become rewarding through “conditioned reinforcement.” Distinct neural circuits are recruited in both acquisition and perpetuation. For adolescents, who are more sensitive to reward than older people, these behaviors more easily become habitual. This formulation should lead to the testing of specific treatment interventions. Clinicians may wish to consider which of their patients' behavioral patterns appear to be habitual and to employ cognitive and behavioral habit-modifying techniques accordingly.

Seeing deep into the brain. A new technique, CLARITY,3 allows visualization of neurons and connections in autopsied brain specimens, including those in long-term storage. First, the specimens are infused with an acrylamide that polymerizes when heated and keeps brain protein structure intact, even after lipids are chemically removed. Lipids, which interfere with visualizing brain structure, are dissolved with a detergent after the acrylamide solidifies.4 The accompanying video displays the remarkably detailed (and beautiful) results of this technique. One example is of aberrant neuronal-fiber connections in an autopsy sample from an 8-year-old autistic child.

Other approaches to studying brain structure and function. The NIH-funded Human Connectome Project plans to use advanced imaging techniques to examine white-matter connectivity.5 In one study, the main techniques are diffusion-spectrum imaging, which allows visualizing layers of fibers, and resting-state functional magnetic resonance imaging (fMRI). The study population of 1200 adults — 300 identical twins, 300 fraternal twins, and 600 nontwin siblings — will enhance the examination of genetic associations. Other measures include electroencephalography and magnetoencephalography. Another study's researchers plan to use high-resolution fMRI.

Sleep and PTSD. This review considers the multiple ways in which sleep disturbances co-associate with post-traumatic stress disorder (PTSD).6 Although disturbances in rapid-eye movement (REM) sleep are common, only equivocal data support the idea that these disturbances are hallmarks of PTSD. Physiological and neurological aspects of nightmares are understudied. Nevertheless, these and other sleep disturbances often seen with PTSD have been associated with lower psychological resilience in some studies. As disturbed sleep is a modifiable risk factor, the author suggests that attention to these issues may accelerate recovery from trauma exposure and PTSD.

Developmental psychobiology of resilience. Resilience is defined in various ways, but generally refers to capacities to adapt swiftly and successfully to adverse psychological and physical events. This thorough review examines resilience as a neurobiological function, including neurocircuitry and gene–environment interactions.7 The animal literature covers resilience in relation to early rearing factors and the impact of stresses across the life span, experience-dependent plasticity, and poststress manipulations to attenuate disturbances. Studies in humans highlight the importance of secure attachments, positive emotions, and their enhancement by modulating reward mechanisms and finding and maintaining a sense of life purpose. The wider social environment also contributes significantly to resiliency.