Attending to anger: Psychological and neurobiological correlates of anger and aggression after military deployment

After military deployment, anger and aggression are frequently reported. US Veterans deployed to Afghanistan and Iraq often report violent offending, and also in Dutch veterans, problems with anger are reported frequently. Literature shows that anger and aggression are common in PTSD and that the presence of anger and aggression has a negative influence on treatment outcome. Therefore, the Dutch Ministry of Defense decided to gather information concerning these difficulties, in order to find markers for the prevention and treatment of anger and aggression. To this aim, the dissertation Attending to Anger, is focused on the prevalence and trajectories of the development of anger problems after military deployment and on the neurobiological background of anger and aggression in military personnel.
The trajectories of anger and hostility before and after deployment were revealed: a low-hostile (remaining low over time), a mild-hostile (remaining mildly hostile over time), an early-hostile group (increases in hostility immediately after deployment) and a late-hostile group (hostility rises 2 years after deployment). It is remarkable that no trajectories with decreases in hostility were found. This raises several important questions: whether anger and aggression are recognized as problems needing interventions, and if so, whether treatments targeting these problems are effective enough.
The neurobiological studies start with a study on the startle response, measured by the eye blink reflex in response to a loud noise. This study shows an exaggerated startle response in the veterans with anger and aggression, indicating a lowered threshold of perceiving threat and heightened physiological arousal. This is further supported by two functional magnetic resonance imaging (fMRI) studies. One study shows enhanced activity in the cuneus and the cingulate cortex in response to proximity of a virtual predator. This indicates that anger and aggression problems are related to heightened arousal and vigilance, which can lead to increased attention to predictors of potential threat, such as proximity. The second fMRI study shows heightened activity in the supplemental motor area, the cingulum and the parietal cortex during the viewing of potentially emotional stimuli. This might reflect increased impulsivity, resulting in a tendency towards motor preparation and enhanced attentional focus on potential threats. A diffusion tensor imaging (DTI) study shows diminished white matter integrity within the arcuate fasciculus. This white matter tract, connecting frontal areas of the brain with parietal areas, has been linked to processes related to understanding, attentional and emotional control. These neurobiological findings offer starting points for treatment, for example by targeting the attentional biases and heightened vigilance by cognitive training, relaxation skills and transcranial direct current stimulation (tDCS).
The title of the dissertation, Attending to anger, has a two-fold interpretation. First, problems with anger and aggression need attention, because these problems arise frequently after deployment. Second, studies into the neurobiology of aggression, point towards stronger attention to potential threat and heightened vigilance. It is essential to recognize the impact of these problems and better understand their nature. The research within this dissertation provides a theoretical basis for further study and directions for treatment.