Bipolar disorder is often a progressive disorder with a high risk of recurrence of depressive and manic episodes1 and with functional disability, decreased quality of life and a reduced life expectancy of 8–12 years.2 It has been hypothesised that the potential pathology of bipolar disorder may be because of impairments in neuroplasticity.3 Brain-derived neurotrophic factor (BDNF) is a member of the neurotropic family and is widely distributed in the central nervous system. Here, BDNF is linked to bipolar disorder.