BDNF and episodic memory in patients with bipolar disorder.

Carta aos editores BDNF and episodic memory in patients with bipolar disorder BDNF e memória episódica em pacientes com transtorno afetivo bipolar Dear Editor, Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, has a whole brain distribution that is highly expressed in key cerebral structures related to psychiatric disorders and cognition such as the amygdala, pre-frontal cortex hypothalamus and hippocampus. 1 The most widely studied polymorphism is Val66Met, which impairs BDNF trafficking and secretion and, according to some studies, Met carriers are more prone to exhibit memory and learning impairments. Recently, the Revista Brasileira de Psiquiatria published a well designed and interesting association study by Tramontina et al. that reported results on Val66Met BDNF polymorphism and performance on the Wisconsin Card Sorting Test in 64 patients with bipolar disorder. 3 The authors found that the percentage of non-perseverative errors was significantly higher in Val/Val carriers, thus contradicting previous findings on cognitive impairment in Met allele carriers. Considering the relationship between BDNF and processes of memory and learning, as well as the existence of episodic deficits in bipolar patients even when euthymic, 4,5 we launched an investigation into the relationship between the Val66Met polymorphism and the performance in verbal and visual episodic memory tasks (COEP UFMG process approval number 018/09). In the initial phase of the study, 63 bipolar disorder subjects in the euthymic phase (as described in Moreira et al. 5), diagnosed according to the DSM IV using a structured interview, underwent the Auditory Verbal Learning Test (RAVLT) and the Rey Complex Figure Test (RCFT). RAVLT measures verbal learning, retention of information and recognition memory. It also measures susceptibility to both proactive and retroactive interference, which is related to attention and executive functions. RCFT measures visio-construction and visual memory. After genotyping, the subjects were grouped according to the presence or absence of Met allele (Val/Val, n = 52; Val/Met + Met/Met, n = 11). The two groups were compared using the Mann-Whitney test (or Chi-square test for categorical variables) and results were considered statistically significant when p < 0.05. We did not find significant differences between the two groups on measures of verbal and visual episodic memory (Table 1). Nevertheless, individuals in the Val/Met + Met/Met group performed significantly worse than individuals in the Val/Val group relative to measurements of susceptibility to proactive interference (z = 2.923; p = 0.003). Our results reinforce the existence of worse cognitive …