Traumatic life events in bipolar disorder: impact on BDNF levels and psychopathology

There is evidence that vulnerability to depression and anxiety disorders is markedly increased by traumatic life events. While childhood abuse has been reported to be associated with poorer outcomes in bipolar disorder, little is known about the neurobiological basis underlying this association. The aim of this study was to ascertain whether bipolar patients who were exposed to a traumatic event or events (TE) have lower brain-derived neurotrophic factor (BDNF) levels and more severe psychopathology as indicated by increased comorbidity and other clinical features when compared to those who were not exposed to TE.

One-hundred and sixty-three consecutively recruited bipolar outpatients were assessed by Structured Clinical Interview for DSM-IV (SCID) and standard protocol in order to evaluation psychopathology and clinical features. The reported TE was assessed using DSM-IV stem criteria for trauma (as defined by A1 and A2 criteria for trauma for post-traumatic stress disorder). Subjects were divided into 2 groups according to presence or absence of lifetime TE. The levels of BDNF, comorbidity and other clinical features were compared between groups.

After adjusting for confounders, results indicated that bipolar patients with a history of TE have alcohol abuse/dependence (p < 0.001), anxiety comorbidity, and lower levels of serum BDNF (p < 0.01) compared to those without a history of TE. There was no difference between the 2 groups in age of onset, presence of psychosis, other substance abuse and dependence, rapid cycling or suicide attempts.

Our findings suggest that TE are associated with significantly increased prevalence of alcohol and anxiety comorbidity as well as lower BDNF levels in bipolar patients. It is possible that a decrease in BDNF levels may account for increased comorbidity, but further prospective studies are required to confirm this.