Could a blood inflammation marker predict who responds to esketamine for depression?

The question

Does the level of interleukin-6 (IL-6), a marker of inflammation measured in blood, predict how well people with treatment-resistant depression respond to esketamine?

What they did

Fourteen adults with treatment-resistant depression took part in a 24-week open-label Phase 2 trial, meaning everyone knew they were getting the drug. They received intranasal esketamine twice a week for 4 weeks, followed by a tapering phase. Depression severity and day-to-day functioning were measured at the start, at week 8 and at week 24, using standard rating scales. Blood levels of IL-6 were measured at the same three time points.

What they found

Depression scores on the Montgomery-Åsberg Depression Rating Scale improved significantly over the course of the study. People with higher IL-6 levels at the start tended to improve more quickly, while lower IL-6 was linked to more severe symptoms and greater disability. IL-6 levels themselves did not change significantly during treatment. The abstract does not report the size of any of these effects in numbers.

The fine print

With only 14 participants and no placebo or comparison group, improvement cannot be attributed to esketamine itself, and the link with IL-6 could easily be a chance finding. The abstract reports no effect sizes, statistics or dose details. Everyone knew they were receiving the drug, which can inflate reported improvement. This summary is based on the abstract alone.

What it means

This is an early, exploratory signal that inflammation markers might one day help predict who responds to esketamine, but the study is far too small to guide any clinical decision.

Evidence grade: Very low. A very small open-label trial of 14 people with no control group or blinding, so the findings are preliminary only.

This summary is based on the study’s published abstract.