Reduced brain-derived neurotrophic factor is associated with childhood trauma experiences and number of depressive episodes in severe mental disorders

Abstract

<p><i>Background - </i>Although several studies have found reduced plasma BDNF levels in patients with severe mental disorders, the sample sizes have been small and have exhibited variation and heterogeneity. Furthermore, long-term neurobiological changes following childhood trauma and clinical severity have been linked to a reduction in BDNF levels. Accordingly, we aim to clarify, using the largest sample size to date, the role of plasma BDNF in individuals with severe mental disorders in relation to the number of episodes, current remission status, and childhood trauma experiences. <p><i>Methods - </i>The study sample comprised 1446 individuals (schizophrenia: SZ [n = 589]; bipolar disorder: BD [n = 254]; and healthy control: HC [n = 603]) all recruited from the same catchment area. A subsample (N = 629) of this larger group had a history of childhood trauma, and some (N = 195) participated in a one-year follow-up study. The level of BDNF in plasma was measured, and childhood trauma was assessed using the Childhood Trauma Questionnaire (CTQ). Diagnoses and episodes were obtained using the Structured Clinical Interview (SCID). <p><i>Results - </i>Patients with SZ or BD had lower levels of plasma BDNF than did the HC group (p = 0.002, p = 0.003, respectively). Within patients, reduced plasma BDNF levels were associated with more depressive episodes (p = 0.04). Longer time in remission after depressive episodes was associated with higher plasma BDNF levels (p = 0.02), and patients reporting childhood sexual abuse exhibited lower plasma BDNF levels (p = 0.049) than patients without sexual abuse. <p><i>Conclusion - </i>Our study confirms that patients with a severe mental disorder exhibit reduced BDNF levels. While the strongest reduction in BDNF was observed in patients reporting childhood sexual abuse, reduced BDNF levels were also associated with more depressive episodes. Accordingly, further studies are warranted to determine whether treatment that increases BDNF levels may be beneficial to these individuals.