Original Research ARTICLE

Front. Integr. Neurosci., 29 July 2013 | http://dx.doi.org/10.3389/fnint.2013.00055

Brain-Derived Neurotrophic Factor (BDNF) protein levels in anxiety disorders: systematic review and meta-regression analysis

Sharain Suliman1*, Sian M. J. Hemmings2 and Soraya Seedat3
  • 1MRC Anxiety Disorders Unit, Department of Psychiatry, Faculty of Medicine and Health Sciences, University of Stellenbosch, Cape Town, South Africa
  • 2Division of Molecular Biology and Human Genetics & Department of Psychiatry, Faculty of Medicine and Health Sciences, University of Stellenbosch, Cape Town, South Africa
  • 3Department of Psychiatry, Faculty of Medicine and Health Sciences, University of Stellenbosch, Cape Town, South Africa

Background: Brain-Derived Neurotrophic Factor (BDNF) is a neurotrophin that is involved in the synaptic plasticity and survival of neurons. BDNF is believed to be involved in the pathogenesis of several neuropsychiatric disorders. As findings of BDNF levels in anxiety disorders have been inconsistent, we undertook to conduct a systematic review and meta-analysis of studies that assessed BDNF protein levels in these disorders.

Methods: We conducted the review using electronic databases and searched reference lists of relevant articles for any further studies. Studies that measured BDNF protein levels in any anxiety disorder and compared these to a control group were included. Effect sizes of the differences in BDNF levels between anxiety disorder and control groups were calculated.

Results: Eight studies with a total of 1179 participants were included. Initial findings suggested that BDNF levels were lower in individuals with any anxiety disorder compared to those without [Standard Mean Difference (SMD) = −0.94 (−1.75, −0.12), p ≤ 0.05]. This was, however, dependent on source of BDNF protein [plasma: SMD = −1.31 (−1.69, −0.92), p ≤ 0.01; serum: SMD = −1.06 (−2.27, 0.16), p ≥ 0.01] and type of anxiety disorder [PTSD: SMD = −0.05 (−1.66, 1.75), p ≥ 0.01; OCD: SMD = −2.33 (−4.21, −0.45), p ≤ 0.01].

Conclusion: Although BDNF levels appear to be reduced in individuals with an anxiety disorder, this is not consistent across the various anxiety disorders and may largely be explained by the significantly lowered BDNF levels found in OCD. Results further appear to be mediated by differences in sampling methods. Findings are, however, limited by the lack of research in this area, and given the potential for BDNF as a biomarker of anxiety disorders, it would be useful to clarify the relationship further.

Keywords: anxiety, BDNF, protein, meta-regression, systematic review

Citation: Suliman S, Hemmings SMJ and Seedat S (2013) Brain-Derived Neurotrophic Factor (BDNF) protein levels in anxiety disorders: systematic review and meta-regression analysis. Front. Integr. Neurosci. 7:55. doi: 10.3389/fnint.2013.00055

Received: 09 April 2013; Paper pending published: 15 April 2013;
Accepted: 08 July 2013; Published online: 29 July 2013.

Edited by:

Sidney A. Simon, Duke University, USA

Reviewed by:

Albino J. Oliveira-Maia, Champalimaud Foundation, Portugal
Anne E. West, Duke University Medical Center, USA

Copyright © 2013 Suliman, Hemmings and Seedat. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.

*Correspondence: Sharain Suliman, MRC Anxiety Disorders Unit, Department of Psychiatry, University of Stellenbosch, PO Box 19063, Tygerberg, 7505 Cape Town, South Africa e-mail: sharain@sun.ac.za