STRESS HAS BEEN widely linked with brain-derived neurotrophic factor (BDNF) modifications but results from the few studies on post-traumatic stress disorder (PTSD) are inconsistent: lower BDNF plasma levels, negative results in cerebrospinal fluid and higher levels in serum have been reported.[1-3]
We investigated BDNF in survivors of the L'Aquila earthquake, along with the post-traumatic spectrum, considering not only full expression but also subthreshold manifestations, that is, partial PTSD.
Thirty-seven medically healthy consecutive outpatients (M/F 13/24; mean age, 45.7 ± 11.7 years) referred for anxiety/affective symptoms manifesting after the earthquake, were recruited 2 years after the event. All were treated with low doses of benzodiazepines and/or antidepressants.
Twenty-two healthy subjects recruited from among those accompanying the outpatients, and who were matched for age and gender (M/F 8/14; mean age, 42.4 ± 11.5 years) were enrolled.
Blood samples were taken between 08.00 and 09.00 AM and processed using ELISA protocol on plasma.
By means of the Structured Clinical Interview officially available in Italy (SCID-I/P), 13 patients were diagnosed as having full PTSD, and 13 as having partial PTSD, that is, fulfilled a subset of the DSM-IV criteria (mean age, 49.9 ± 10.2 years; M/F 3/10; mean age, 44.4 ± 13.6 years, M/F 4/9); 11 patients (mean age, 42.3 ± 10.3 years; M/F 6/5) were diagnosed as not having PTSD but instead were diagnosed as having depressive episode (n = 8) or panic attack (n = 3). No differences in gender distribution or age were observed.
BDNF level was as follows: full PTSD subjects 3473.3 ± 2073.2 pg/mL; partial PTSD, 6180.9 ± 2348.3 pg/mL; clinical sample without PTSD, 3650.6 ± 1648.2 pg/mL; controls, 6172.9 ± 3899.3 pg/mL. Kruskal–Wallis test indicated significant difference (χ2 = 17.20, d.f. = 3, P < 0.001); post-hoc planned Mann–Whitney test indicated lower BDNF for subjects with full-blown or no PTSD than subjects with partial PTSD (Z = 3.51, P < 0.0005 and Z = 3.10, P < 0.005) and controls (Z = 2.56, P < 0.01 and Z = 2.29, P < 0.05) and no difference between partial PTSD and controls.
Reduced BDNF in full PTSD is in agreement with Dell'Osso et al. The BDNF finding in patients with partial PTSD is in line with Bonne et al., who found no difference between patients with moderate PTSD severity and controls. Hauck et al. reported that BDNF was elevated in subjects at early stages of trauma showing less severe symptoms. Together with the current finding that patients with partial PTSD had higher BDNF levels, we can hypothesize that the higher plasma level of BDNF would somehow have a neuroprotective role against the expression of full PTSD.
The sample size was relatively small, but all patients were triggered by a unique trauma, had a similar low drug dosage and none presented comorbid psychiatric diagnoses.