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.
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.”
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