Comparison of serum bdnf levels and neurocognitive functions in patients with bipolar disorder, first degree relatives and healthy controls

Objective: Bipolar disorder is a chronic illness characterized by manic and depresive relapses. Its etiology is still unknown. Neurotrophins and neurocognitive functions are possible endohenotype candidates for bipolar disorder. The aim of this study is to examine serum BDNF levels and neurocognitive functions in euthymic patients and their first degree relatives in comparison to healthy controls as candidates of phenotypes.Method: Thirty euthymic patients with bipolar disorder type I, their first degree relatives (n=19) and 24 sex, age and education-wise matched healthy controls were enrolled in the study. Serum BDNF levels were measured using a sandwich-ELİSA kit. Patiens were evaluated with Structured Clinical Interview for DSM-IV-TR (SCID-I), Young Mania Scale (YMRS), Hamilton Depression Scale-17 (HAM-D 17), Clinical Global Impression Scale for Bipolar Disorder (BP-CGI) and Global Assessment of Functioning Scale (GAF). A large neurocognitive battery was used for neurocognitive assessment. Kruskal Wallis, Mann Whitney-U, chi-square, Spearman and Pearson correlation analysis were used for statistical analysis.Results: Serum BDNF levels showed no difference among the three groups. Both patients and their first degree relatives performed poorer on the attention, executive and verbal memory functions compared to healthy controls. The first degree relatives scored between the patients and healthy controls on these neurocognitive tests. There was no correlation between BDNF levels and neurcognitive test results in the whole group.Conclusion: The results of this study show that serum BDNF level does not seperate patients with bipolar disorder I either from their fisrt degree relatives or from healthy controls when they are euthymic whereas some neurocognitive functions seem to be able to differentiate patients and first degree relatives from healthy controls. Given that an endophenotype is expected to exist during well being as well as during ill periods, BDNF doesn?t seem to meet the criteria for being an endophenotype for bipolar disorder. However, decline in neurcognitive functions can be more appropriate endophenotype candidate for bipolar disorder due to its existence in the euthymic patients and in their first degree relatives.