Posted 11.28.2017 | by AMRA

Are there biological markers for depression that continue to exist even when the depressive symptoms go away? One possible candidate for such a marker is an electroencephalographic (EEG) waveform called error related negativity (ERN).

ERN is a sharp negative wave that occurs whenever people make a mistake while performing a task. The waveform begins at the start of the error and peaks shortly thereafter. ERNs occur even when people are not consciously aware of having made a mistake.

In healthy individuals, larger ERNs are associated with better executive and attentional control and enhanced self-regulation. People with depression, however, typically have smaller ERNs. When their depressive symptoms improve with treatment, their ERNs continue to be smaller than those of healthy individuals. This raises the possibility that smaller ERNs reflect an underlying biological vulnerability to depression.

Fissler et al. [Cognitive and Affective Behavioral Neuroscience] sought to discover whether brief mindfulness training could help improve ERNs in people with chronic depression.

The researchers recruited a sample of 68 patients (average age = 39 years; 61% female) with histories of chronic or recurring major depression who were currently depressed. They also recruited a comparison sample of 25 healthy controls.

Participants had their EEGs recorded while performing a sustained attention task. A series of digits were displayed individually on a computer screen and participants were told to push the keyboard space bar whenever they saw the digits “0” through “2” and “4” through “9,” but to withhold responding whenever they saw a “3.” The researchers then recorded the total number of errors made to the number “3” and the average ERN magnitude when those errors were made.

Following the initial assessment, members of the depressed sample were randomly assigned to either two weeks of mindfulness training or resting control training. Both trainings were delivered in a series of three 1.5-hour individual sessions accompanied by daily home practice.

The mindfulness training required 25 minutes of formal guided home meditation practice twice a day. The meditative practices followed the sequence typically used in Mindfulness-Based Cognitive Therapy. Control group participants engaged in two 25-minute rest periods a day. They were told that the rest would reduce stress and help them to disengage from their negative thinking.

Mindfulness participants believed their intervention to be significantly more plausible than control group participants. Both groups of participants with depression repeated the EEG-monitored sustained attention task following their respective interventions.

The researchers analyzed data for 59 depressed participants and 18 healthy controls who made multiple mistakes on the sustained attention task. Depressed patients made significantly (η2= .12) more mistakes (mean = 26) than healthy controls (mean = 16).

Depressed patients also had significantly smaller baseline ERNs than healthy controls. The magnitude of depressed patients’ ERNs were uncorrelated with the severity of their psychiatric symptoms.

Participants with depression in the mindfulness group showed both greater psychiatric symptom improvement (η2= .23) and greater ERN improvement in their frontal brain regions than did participants with depression in the control group (η2= .08). ERN improvement was uncorrelated with improvements in psychiatric symptoms.

The results show that a brief mindfulness intervention can improve ERN in people with depression. This is important because a larger ERN is associated with better cognitive control and self-regulation, whereas a smaller ERN may indicate a vulnerability to depression. It’s possible that enhancing ERN may lower the risk of future depressive recurrence.

The fact that participants found the mindfulness group more creditable than the control group raises the possibility of different group motivation levels.

Reference:

Fissler, M., Winnebeck, E., Schroeter, T. A., Gummbersbach, M., Huntenburg, J. M., Gärtner, M., & Barnhofer, T. (2017). Brief training in mindfulness may normalize a blunted error-related negativity in chronically depressed patients. Cognitive, Affective, & Behavioral Neuroscience.

[Link to abstract]