Reward processing after catecholamine depletion in unmedicated, remitted subjects with major depressive disorder

We investigated whether performance on a reward processing task differs between fully remitted patients with major depressive disorder (MDD) and healthy control subjects after catecholamine depletion.

Seventeen unmedicated subjects with remitted MDD (RMDD) and 13 healthy control subjects underwent catecholamine depletion with oral alpha-methyl-para-tyrosine (AMPT) in a randomized, placebo-controlled, double-blind crossover study. The main outcome measure was the reaction time on the monetary incentive delay (MID) task.

A diagnosis x drug interaction was evident (p = .001), which was attributable to an increase in reaction time across all incentive levels after AMPT in RMDD subjects (p = .001) but no significant AMPT effect on reaction time in control subjects (p = .17). There was no drug x diagnosis interaction on control tasks involving working memory or attention. In the RMDD sample the AMPT-induced depressive symptoms correlated with AMPT-induced changes in reaction time at all incentive levels of the MID task (r values = .58-.82, p < .002).

Under catecholamine depletion the RMDD subjects were robustly differentiated from control subjects by development of performance deficits on a reward processing task. These performance deficits correlated directly with the return of depressive symptoms after AMPT administration. The sensitivity of central reward processing systems to reductions in brain catecholamine levels thus seems to represent a trait-like marker in MDD.