Fragility of reward vs antifragility of defense brain systems in drug dependence.

Drug dependence is a debilitating disorder, affecting 30 million people worldwide. In this short review we discuss about the plasticity changes in the reward and defense brain systems induced by early-life psychosocial stressful experiences. Such changes may render persons more vulnerable to illicit drugs use, facilitating behaviors of abuse and development of addiction. We propose that underlying plasticity changes render brain reward system as increasingly fragile because of tolerance and other physiological effects that reduce responsiveness with repeated use. In contrast, we propose that brain defense system makes maintain antifragile mechanisms that generate more robust responses with the prolonged consumption of drugs. Investigating the underlying mechanisms of these brain plasticity changes may advance the development of more efficacious pharmacologic and psychotherapeutic approaches to rehabilitate patients and more efficacious prevention policies to protect children from stressful experiences.