New research in the scientific journal Biological Psychology provides evidence that depression is linked to abnormal inhibitory control, or willpower.

“As a clinical psychology doctoral student, I have worked with many clients presenting with major depressive disorder (MDD) or depressive symptoms,” remarked study author Erin Palmwood of the University of Delaware.

“I noticed that problems with impulsivity seem to come up for many of these clients, particularly surrounding self-harm and suicide attempts, but realized that there was very little research out there on the mechanisms by which failures of inhibition occur for people with depression.”

“As my laboratory often uses electroencephalography (EEG) to examine the different aspects of inhibitory control, this project was a natural extension of our ongoing work on inhibition and psychopathology,” Palmwood explained.

The study used EEG to examine the brain activity of 15 people with major depressive disorder while they completed a stop-signal reaction-time task — a test of inhibitory control. Another 15 people without depression served as a control group.

The participants were given a “go” signal in the form of an arrow pointing left or right — and pressed a corresponding computer key as quickly as possible. In one-third of the trials, a “stop” signal appeared in the form of a red circle, indicating the participant should withhold their key press.

Both groups were the same when it came to identifying the need to exert inhibitory control. But the depressed participants displayed abnormalities in the conflict resolution phase of inhibitory control.

“I hope that the average person takes away that (1) depression is associated with problems with inhibitory control, and (2) the portion of the inhibitory control process that is impacted in depression is the ‘brake’ process, such that people with depression are able to notice when they need to inhibit a response but have difficulty actually implementing that inhibition,” Palmwood told PsyPost.

The study has some limitations.

“As the sample used was predominantly female and consisted of only college students, we need to know whether these inhibitory control deficits are specific to college-aged women or if they are present among men, older adults, children, etc,” Palmwood said.

“Additionally, computer-based measures of inhibitory control (like the one used in this study) are pretty different from “real world” situations in which inhibitory control is needed, and it can therefore be challenging to find the group differences (e.g., between depressed and non-depressed people) in inhibitory control ability on these tasks that we might see outside of the lab. It is therefore important to use methods such as direct observation or economical momentary assessment to examine inhibitory control in more naturalistic settings.”

The study, “Electrophysiological Indicators of Inhibitory Control Deficits in Depression“, was co-authored by Jason W. Krompinger and Robert F.Simons.