According to a study recently published in Psychiatric Research, a history of psychomotor retardation (PmR) is indicative of altered reward-based reinforcement learning in patients with remitted major depressive disorder (rMDD).

Impaired reward-based reinforcement learning (RL) is common in patients with MDD, but research is sparse regarding which aspects of reward-based RL are disrupted in MDD patients in remission. The researchers decided to explore the neurobiology related to reward-based RL and PmR in patients in remission from MDD.

The researchers recruited 504 adults aged 18 to 30 who had a sibling in the same age range who also volunteered to participate. Participants were evaluated for MDD and PmR symptoms and divided into 3 groups: (1) rMDD with PmR symptoms during their past major depressive episode (2) rMDD without PmR symptoms and (3) controls with no history of MDD or PmR.


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Psychomotor speed did not vary between rMDD groups. The groups also did not differ in their Probabilistic Reward Task test.

“History of PmR during a past episode of MDD predicted current alterations in reward-based RL,” the researchers concluded. “This suggests that difficulties in rMDD with reward-based RL are not merely the result of psychomotor slowing. …There is evidence that corticostriatal circuitry and dopaminergic functioning that supports reward-based RL are disrupted in PmR.”

Psychomotor symptom history was based on a retrospective clinical assessment. In addition, the study did not clarify “whether abnormal reward-based RL processing reflects a scar of past MDD episodes that contained psychomotor symptoms or a trait-like deficit that preceded episodes,” the researchers stated. Participants were recruited from a larger study, which may have also affected the data.

Despite the limitations, the researchers conclude, “targeting residual PmR symptoms in individuals with a history of MDD and/or reward-based RL in individuals with a history of PmR may help to prevent relapse into future depressive episodes.”

Reference

Letkiewicz AM, Cochran AL, Mittal VA, Walther S, Shankman SA. Reward-based reinforcement learning is altered among individuals with a history of major depressive disorder and psychomotor retardation symptoms. J Psychiatr Res. 2022;152:175-181. doi:10.1016/j.jpsychires.2022.06.032