From the article:
Prior studies have suggested that depressed people with evidence of high inflammation are less likely to respond to traditional treatments for the disorder, including anti-depressant medications and psychotherapy. This study was designed to see whether blocking inflammation would be a useful treatment for either a wide range of people with difficult-to-treat depression or only those with high levels of inflammation.
Study participants all had major depression and were moderately resistant to conventional antidepressant treatment. Each participant was assigned either to infliximab or to a non-active placebo treatment.
When investigators looked at the results for the group as a whole, no significant differences were found in the improvement of depression symptoms between the drug and placebo groups. However, when the subjects with high inflammation were examined separately, they exhibited a much better response to infliximab [TNF inhibitor] than to placebo.
Inflammation in this study was measured using a simple blood test that is readily available in most clinics and hospitals and measures C-reactive protein or CRP. The higher the CRP, the higher the inflammation, and the higher the likelihood of responding to the drug.