Baseline symptom severity predicts serotonin transporter change during psychotherapy in patients with major depression

Aims The role of the serotonin transporter (SERT) in the pathophysiology of depression is unclear and only a few follow‐up studies exist. Our aim was to measure changes in SERT availability during psychodynamic psychotherapy in patients with major depression over a follow‐up time of 12 or 18 months. Methods The patients were studied with iodine‐123 labelled 2β‐carbomethoxy‐3β‐(4‐iodophenyl) serial single‐photon emission tomography imaging and clinical rating scales of symptoms. Results Changes in SERT availability had no correlation with the change of symptoms, but the change of SERT availability during psychotherapy in the midbrain was predicted by the baseline severity of the clinical symptoms measured by the Symptom Checklist Depression Scale and the Symptom Checklist Global Severity Index. With cut‐off values applied, it was found that SERT availabilities increased in patients with high baseline symptoms, and decreased in patients with low baseline symptoms. Conclusions Together with our earlier finding of decreased SERT in patients with depression, these results indicate a state‐dependent and possibly a compensatory role of decreased SERT availability in depression.