Childhood Maltreatment and Mechanisms of Vulnerability Within Anhedonia and Depression
Anhedonia is one of the defining features of Major Depressive Disorder (MDD), and may be characteristic of an especially severe depression. Because MDD is highly heterogeneous, anhedonia may represent an easier target for research on how childhood maltreatment is associated with MDD and anhedonia and on the underlying mechanisms of dysfunction within this disorder. The goal of the current study is to test the hypothesis that the association between childhood maltreatment and anhedonia is mediated by two endophenotypes: (a) blunted neuroendocrine response to stress, and (b) blunted responsivity to reward. Further, consistent with the related neurobiological underpinnings of threat and reward systems, we hypothesize that in our full sample, individual differences in stress reactivity will be correlated with individual differences in reward responsivity. The current study includes 89 adults (39 with MDD, 47 non-depressed) who were well-characterized in terms of their diagnostic and symptom profiles, and who participated in a laboratory stress challenge (the Trier Social Stress Task; TSST) and a computerized Probabilistic Reward Task (PRT). Our hypothesized mediation model was not supported by the results. However, I did find that blunted reward learning was correlated with blunted stress reactivity. Further, different forms of childhood maltreatment were preferentially associated with different symptoms of anhedonia. Contrary to hypotheses, I also found that within the depressed group, childhood maltreatment, depression severity, and anhedonia were positively correlated with response bias on the PRT. Also contrary to hypotheses, within the depressed group stress reactivity was positively associated with anhedonic symptoms, although these results were not statistically significant. Although our overall model was not supported by the results, my findings suggest that reward responsivity, stress reactivity, and anhedonia remain important research targets in understanding the etiology of MDD. These findings also help to shed light on the negative outcomes associated with childhood maltreatment.