Lower levels of brain‐derived neurotrophic factor are associated with melancholic psychomotor retardation among depressed inpatients

Objectives Melancholic depression is a type of depression which is closely related to biological variables than are other types of depression. Its clinical features can be assessed using six items on the Hamilton Depression Rating Scale (HAM‐D6). Previous studies have shown, using item response theory, that the symptom depressed mood is the least severe melancholic feature; work and activities, somatic symptoms and psychic anxiety are of moderate severity; and feelings of guilt and psychomotor retardation are the most severe. We aimed to evaluate whether the more severe melancholic signs or symptoms were associated with decreases in brain‐derived neurotrophic factor (BDNF) levels. Methods A total of 151 severely depressed inpatients had their BDNF levels analyzed by comparing those who presented with each HAM‐D6 melancholic feature to those for whom the HAM‐D6 feature was absent, using multiple linear regressions. The levels of BDNF of patients who presented with each melancholic feature were also compared with those of 100 healthy controls. Results Depressed patients' median BDNF level was 44.06 ng/mL (interquartile range [IQR]: 33.99‐62.4 ng/mL), and controls' median BDNF level was 65.22 ng/mL (IQR: 49.87‐76.08 ng/mL) (P