Severe depression is associated with decreased levels of serum brain-derived neurotrophic factor in type 2 diabetes patients in Ghana

Objectives: Type 2 diabetes (T2DM) has been associated with several mental disorders including depression. Brain-derived neurotrophic factor (BDNF) has been suggested as a mediator between T2DM and depression. We investigated the association between BDNF and depression in T2DM patients in a primary health facility in Ghana. Methods: In a case-control study design, depression was assessed using the Patient's Health Questionnaire (PHQ-9) in 200 T2DM patients and 160 non-diabetic controls. A structured questionnaire was used to collect data on lifestyle, socio-demography and medical history. Fasting blood samples were collected from each participant to measure plasma lipid profile and serum BDNF levels. Results: T2DM patients had higher levels of depression (31.5% vs 10.6, p < 0.001) and lower serum levels of BDNF (22.8 +/- 4.6 vs 34.6 +/- 10.6, p < 0.001) compared to non-diabetic controls. In non-diabetic controls, those with depression had low levels of serum BDNF compared to their non-depressed counterparts (38.9 +/- 10.1 vs 32.3 +/- 9.9 ng/ml, p = 0.038), but in T2DM patients, no difference in serum BDNF levels was observed in those with and without depression. Severe depression in T2DM patients [OR (95% CI): 0.81 (0.57-0.97), p = 0.042] and mild depression in non-diabetic controls [0.84 (0.6-0.95), p < 0.001] were associated with reductions in serum BDNF levels. Conclusions: In our study sample, T2DM patients had a high burden of depression and low levels of BDNF compared to the non-diabetic controls. T2DM with severe depression and non-diabetic controls with mild depression had significant reduction of serum BDNF levels.