There is accumulating evidence that the error-related negativity (ERN), an event-related potential elicited after erroneous actions, is altered in different psychiatric disorders and may help to guide treatment options. Thus, the ERN is a promising candidate as a psychiatric biomarker. Basic methodological requirements for a biomarker are that their measurements are standardised and reliable. The aim of the present study was to establish ERN acquisition in a reliable, time-efficient and patient-friendly way for use in clinical practice.

Healthy subjects performed a speeded Eriksen Flanker Task that increases the number of errors. In a test–retest design (N = 14) with two sessions separated by 28 days we assessed the reliability of the ERN. To ensure external validity, we aimed to replicate previously reported correlation patterns of ERN amplitude with (A) number of errors and (B) negative affect. In order to optimise the clinical use of the task, we determined to which extent the task can be shortened while keeping reliability >0.80.

We found excellent reliability of the ERN (intraclass correlation coefficients = 0.806–0.947) and replicated ERN correlation patterns. The task can be halved to a patient-friendly length of 200 trials (recorded in 8 min) keeping reliability >0.80.

The modified task provides reliable and efficient recording of the ERN, facilitating its use as a psychiatric biomarker.