Brain-derived neurotrophic factor in traumatic brain injury, post-traumatic stress disorder, and their comorbid conditions: role in pathogenesis and treatment.

As US military service members return from the wars in Iraq and Afghanistan with elevated rates of traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD), attention has been increasingly focused on TBI/PTSD comorbidity, its neurobiological mechanisms, and novel and effective treatment approaches. TBI and PTSD, and their comorbid conditions, present with a spectrum of common clinical features such as sleep disturbance, depression, anxiety, irritability, difficulty in concentrating, fatigue, suicidality, chronic pain, and alterations in arousal. These TBI and PTSD disorders are also thought to be characterized by overlapping neural mechanisms. Both conditions are associated with changes in hippocampal, prefrontal cortical, and limbic region function because of alterations in synaptogenesis, dendritic remodeling, and neurogenesis. Neural changes in TBI and PTSD result from pathophysiological disturbances in metabolic, cytotoxic, inflammatory, and apoptic processes, amongst other mechanisms. Neurotrophins have well-established actions in regulating cell growth and survival, differentiation, apoptosis, and cytoskeleton restructuring. A body of research indicates that dysregulation of neural brain-derived neurotrophic factor (BDNF) is found in conditions of TBI and PTSD. Induction of BDNF and activation of its intracellular receptors can produce neural regeneration, reconnection, and dendritic sprouting, and can improve synaptic efficacy. In this review, we consider treatment approaches that enhance BDNF-related signaling and have the potential to restore neural connectivity. Such treatment approaches could facilitate neuroplastic changes that lead to adaptive neural repair and reverse cognitive and emotional deficits in both TBI and PTSD.