Animal models suggest that chronic unpredictable stress blunts hedonic capacity4, consequently producing a depression-like phenotype5. Similarly, in human studies, perceived stress has been found to increase negative affect and anhedonia6 and to contribute to reduced reward responsiveness,7 even after controlling for depressed mood. Childhood exposure to physical abuse may be one such potent stressor. This form of stress, often perpetrated by a parent or caregiver, can be inescapable and have virulent short- and long-term effects on the physical and mental well-being of the child8;9. However, not all children exposed to childhood abuse and maltreatment develop problems. For instance, Caspi and colleagues10 found that carriers of the high activity allele of a polymorphism in the monoamine oxidase A (MAOA) gene were buffered from the pathogenic influence of severe childhood maltreatment on antisocial behavior and violence during early adulthood. Likewise, albeit controversially11;12, multiple studies have found that carriers of the short, putatively less functional, allele of the serotonin transporter gene (SLC6A4) are at greater risk for depression upon exposure to stress, particularly childhood maltreatment13. Studies such as this point to the existence of possible biological and environmental mechanisms for stress adaptation.
