The suicide rates among asthmatic patients are higher than among the general population. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family and is strongly associated with suicide pathogenesis. BDNF also plays an important role in neuroimmune reactions in allergic diseases such as asthma. Therefore, we hypothesize that alterations of BDNF levels in the brain may explain the increased suicide rates among asthmatic patients. (C) 2011 Elsevier Ltd. All rights reserved.