Serum neurotrophic factors in adolescent depression: gender difference and correlation with clinical severity

Brain derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3) and glial cell line derived neurotrophic factor (GDNF) play critical role in growth, differentiation, maintenance and synaptic plasticity in neuronal systems which is more relevant in adolescence. The present study was undertaken to verify the 'neurotrophin hypothesis' in adolescent depression by (i) comparing serum concentrations of neurotrophic factors in depression patients and healthy control, and (ii) analyzing correlations between clinical severity and serum neurotrophin levels.

Eighty four adolescent (aged 13-18 years) depressed patients (56 males; 60 medication free/naive) and 64 healthy controls (39 males) were recruited. Severity of depression was measured by Beck's depression inventory, and anxiety by state-trait anxiety inventory. Measurement of serum neurotrophins was done by ELISA.

Adolescents with depression had significantly lower levels of BDNF: mean diff. (95% C.I.): 2093.9 (1074.0, 3113.9), NGF: 813.3 (343.1, 1283.6) and GDNF: 158.8 (77.2, 240.4) compared to controls. On gender based analysis female controls had significantly increased trait anxiety scores [-1.1 (-1.8, -0.1)], as compared to control males. In the patient group, female patients had far lower level of NGF: 919.6 (210.9, 1628.3) and NT-3: 1288.8 (145.4, 2432.3) compared to male. BDI-II score showed a statistically significant (p<0.01) negative correlation with all four neurotrophins in male patients while in female patients such negative correlation was observed only with NGF and GDNF (p<0.01).

The study is cross-sectional from a tertiary care hospital.

The novelty of the study lies in its large number of exclusively adolescent depression patients showing significant reduction of BDNF, NGF and GDNF serum levels as compared to controls. A gender bias with much reduction in female has also been recorded.