Reduced hedonic capacity in major depressive disorder: evidence from a probabilistic reward task.
OBJECTIVE
Anhedonia, the lack of reactivity to pleasurable stimuli, is a cardinal feature of depression that has received renewed interest as a potential endophenotype of this debilitating disease. The goal of the present study was to test the hypothesis that individuals with major depression are characterized by blunted reward responsiveness, particularly when anhedonic symptoms are prominent.


METHODS
A probabilistic reward task rooted within signal-detection theory was utilized to objectively assess hedonic capacity in 23 unmedicated subjects meeting DSM-IV criteria for major depressive disorder (MDD) and 25 matched control subjects recruited from the community. Hedonic capacity was defined as reward responsiveness - i.e., the participants' propensity to modulate behavior as a function of reward.


RESULTS
Compared to controls, MDD subjects showed significantly reduced reward responsiveness. Trial-by-trial probability analyses revealed that MDD subjects, while responsive to delivery of single rewards, were impaired at integrating reinforcement history over time and expressing a response bias toward a more frequently rewarded cue in the absence of immediate reward. This selective impairment correlated with self-reported anhedonic symptoms, even after considering anxiety symptoms and general distress.


CONCLUSIONS
These findings indicate that MDD is characterized by an impaired tendency to modulate behavior as a function of prior reinforcements, and provides initial clues about which aspects of hedonic processing might be dysfunctional in depression.
Pizzagalli
Diego A
DA
Department of Psychology, Harvard University, 1220 William James Hall, 33 Kirkland Street, Cambridge, MA 02138, USA. dap@wjh.harvard.edu
Iosifescu
Dan
D
Hallett
Lindsay A
LA
Ratner
Kyle G
KG
Fava
Maurizio
M
D000328:Adult; D000342:Affective Symptoms / Q000175:diagnosis* / Q000523:psychology; D035061:Control Groups; D003865:Major Depressive Disorder / Q000175:diagnosis* / Q000523:psychology; D039721:Diagnostic and Statistical Manual of Mental Disorders; D004644:Emotions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D010641:Phenotype; D011336:Probability; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D012054:Reinforcement, Psychology; D012201:Reward; D017603:Signal Detection, Psychological; D013647:Task Performance and Analysis