Reduced platelet BDNF level in patients with major depression.

Serum and plasma brain-derived neurotrophic factor (BDNF) levels as well as brain BDNF have previously been shown to be decreased in patients with major depressive disorder (MDD). We explored whether platelet BDNF levels, circulating stored BDNF, would be lower in MDD patients than in normal controls. BDNF levels were examined in platelet-rich plasma (PRP) and platelet-poor plasma (PPP) in 20 hospitalized non-suicidal MDD patients, 20 recent-suicidal MDD patients, and 20 normal controls. Platelet BDNF content was calculated by subtracting PPP BDNF level from PRP BDNF level, and dividing the result by the total platelet count, and it was expressed as pg/10(6) platelets. Individuals were evaluated using a Structured Clinical Interview for DSM-IV and a Hamilton Depression Rating Scale. Platelet BDNF contents were significantly lower in non-suicidal patients (3.09+/-2.53 pg/10(6) platelets) and recent-suicidal MDD patients (3.16+/-1.99 pg/10(6) platelets) than in healthy controls (6.17+/-2.64 pg/10(6) platelets) (p<0.01). However, platelet BDNF contents had no significant differences between non-suicidal and recent-suicidal patients. PRP BDNF levels were also significantly lower in non-suicidal and suicidal MDD patients than in healthy controls (p=0.029), while PPP BDNF had no significant difference between 3 groups (p=0.971). Our findings suggest that there is a decrease in the platelet BDNF of patients with major depression. Reduced platelet BDNF contents as circulating stored BDNF could be associated with lower serum BDNF level in patients with major depression.