Serum levels of brain-derived neurotrophic factor in major depressive disorder: state-trait issues, clinical features and pharmacological treatment

Serum brain-derived neurotrophic factor levels and psychotic symptoms in heroin dependence

OBJECTIVES

Psychotic symptoms are commonly observed among heroin users. Low serum brain-derived neurotrophic factor (BDNF) levels have been reported in schizophrenia and psychosis; however, studies assessing the relationship between serum BDNF levels and psychotic symptoms in heroin dependence are lacking.

METHOD

A total of 31 heroin-dependent patients who had never experienced psychotic symptoms during heroin consumption and 21 patients with a history of psychotic symptoms were consecutively recruited. We measured by enzyme-linked immunosorbent assay (ELISA) serum BDNF levels during early abstinence. A gender- and age-matched sample of healthy controls was also recruited and underwent measurement of BDNF.

RESULTS

BDNF levels were significantly lower in patients with psychotic symptoms than in those without psychotic symptoms (P<0.001). BDNF levels were not found to be correlated with sex, age, age of onset, duration of heroin use, average daily dose of heroin use, frequency of heroin use, SDS scores, BAI scores and BDI scores in the psychotic subsamples (all P>0.05).

CONCLUSIONS

Our findings suggest that heroin-dependent patients with psychotic symptoms share some of the neurotrophic insult that characterizes schizophrenia and psychosis.

7,8-Dihydroxyflavone reduces sleep during dark phase and suppresses orexin A but not orexin B in mice

Brain-derived neurotrophic factor (BDNF) binds to Tropomyosin-receptor-kinase B (TrkB) receptors that regulate synaptic strength and plasticity in the mammalian nervous system. 7,8-Dihydroxyflavone (DHF) is a recently identified small molecule Trk B agonist that has been reported to ameliorate depression, attenuate the fear response, improve memory consolidation, and exert neuroprotective effects. Poor and disturbed sleep remains a symptom of major depressive disorder and most current antidepressants affect sleep. Therefore, we conducted sleep/wake recordings and concomitant measurement of brain orexins, endogenous peptides that suppress sleep, in mice for this study. Baseline polysomnograph recording was performed for 24 h followed by treatment with either 5 mg/kg of DHF or vehicle at the beginning of the dark phase. Animals were sacrificed the following day, one hour after the final treatment with DHF. Orexin A and B were quantified using ELISA and radioimmunoassay, respectively. Total sleep was significantly decreased in the DHF group, 4 h after drug administration in the dark phase, when compared with vehicle-treated animals. This difference was due to a significant decrease of non-rapid eye movement sleep, but not rapid eye movement sleep. DHF increased power of alpha and sigma bands but suppressed power of gamma band during sleep in dark phase. Interestingly, hypothalamic levels of orexin A were also significantly decreased in the DHF group (97 pg/mg) when compared with the vehicle-treated group (132 pg/mg). However, no significant differences of orexin B were observed between groups. Additionally, no change was found in immobility tests.

Plasma brain-derived neurotrophic factor levels in patients suffering from post-traumatic stress disorder

A number of studies have been done to investigate the role of brain-derived neurotrophic factor (BDNF) in patients with post-traumatic stress disorder (PTSD). In this study we aimed to test the relationship between plasma BDNF levels and PTSD. We solicited 65 subjects having recently experienced road traffic accidents (RTA) conforming to screening criteria. They were given follow-up examinations after one month, three months, and six months. PTSD was diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-R-TR, American Psychiatric Association, 2000) using the Mini International Neuropsychiatric Interview (MINI). All participants were divided into two groups: a group with PTSD and a group without PTSD. There were no significant differences in plasma BDNF levels between the two groups at either the 48h or six-month examination. Within the PTSD group, no significant differences were found in plasma BDNF levels between the two examinations. BDNF levels in those without PTSD showed a higher trend over time after trauma. Higher BDNF levels may be an important protective factor for the prevention of traumatized subjects from developing PTSD.

Epigenetic mechanisms underlying the role of brain-derived neurotrophic factor in depression and response to antidepressants

Major depressive disorder (MDD) is a devastating neuropsychiatric disorder encompassing a wide range of cognitive and emotional dysfunctions. The prevalence of MDD is expected to continue its growth to become the second leading cause of disease burden (after HIV) by 2030. Despite an extensive research effort, the exact etiology of MDD remains elusive and the diagnostics uncertain. Moreover, a marked inter-individual variability is observed in the vulnerability to develop depression, as well as in response to antidepressant treatment, for nearly 50% of patients. Although a genetic component accounts for some cases of MDD, it is now clearly established that MDD results from strong gene and environment interactions. Such interactions could be mediated by epigenetic mechanisms, defined as chromatin and DNA modifications that alter gene expression without changing the DNA structure itself. Some epigenetic mechanisms have recently emerged as particularly relevant molecular substrates, promoting vulnerability or resilience to the development of depressive-like symptoms. Although the role of brain-derived neurotrophic factor (BDNF) in the pathophysiology of MDD remains unclear, its modulation of the efficacy of antidepressants is clearly established. Therefore, in this review, we focus on the epigenetic mechanisms regulating the expression of BDNF in humans and in animal models of depression, and discuss their role in individual differences in vulnerability to depression and response to antidepressant drugs.

Pathophysiology of major depressive disorder: mechanisms involved in etiology are not associated with clinical progression

Meta-analyses support the involvement of different pathophysiological mechanisms (inflammation, hypothalamic-pituitary (HPA)-axis, neurotrophic growth and vitamin D) in major depressive disorder (MDD). However, it remains unknown whether dysregulations in these mechanisms are more pronounced when MDD progresses toward multiple episodes and/or chronicity. We hypothesized that four central pathophysiological mechanisms of MDD are not only involved in etiology, but also associated with clinical disease progression. Therefore, we expected to find increasingly more dysregulation across consecutive stages of MDD progression. The sample from the Netherlands Study of Depression and Anxiety (18-65 years) consisted of 230 controls and 2333 participants assigned to a clinical staging model categorizing MDD in eight stages (0, 1A, 1B, 2, 3A, 3B, 3C and 4), from familial risk at MDD (stage 0) to chronic MDD (stage 4). Analyses of covariance examined whether pathophysiological mechanism markers (interleukin (IL)-6, C-reactive protein (CRP), cortisol, brain-derived neurotrophic factor and vitamin D) showed a linear trend across controls, those at risk for MDD (stages 0, 1A and 1B), and those with full-threshold MDD (stages 2, 3A, 3B, 3C and 4). Subsequently, pathophysiological differences across separate stages within those at risk and with full-threshold MDD were examined. A linear increase of inflammatory markers (CRP P=0.026; IL-6 P=0.090), cortisol (P=0.025) and decrease of vitamin D (P<0.001) was found across the entire sample (for example, from controls to those at risk and those with full-threshold MDD). Significant trends of dysregulations across stages were present in analyses focusing on at-risk individuals (IL-6 P=0.050; cortisol P=0.008; vitamin D P<0.001); however, no linear trends were found in dysregulations for any of the mechanisms across more progressive stages of full-threshold MDD. Our results support that the examined pathophysiological mechanisms are involved in MDD's etiology. These same mechanisms, however, are less important in clinical progression from first to later MDD episodes and toward chronicity.

Neurotrophic factors in depression in response to treatment

BACKGROUND

Brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor A (VEGF) have been suggested to play a role in the pathophysiology of depression. The neurotrophic model of depression hypothesises that the serum level of e.g. BDNF is decreased during depression and increased in response to treatment. The aim of the present study was to investigate BDNF and VEGF as potential predictors of response to antidepressant treatment.

METHODS

We investigated the longitudinal associations between depression scores and serum levels of these neurotrophic factors during antidepressant treatment in 90 individuals with depression of at least moderate severity. Serum levels were measured at baseline and after 8 and 12 weeks of treatment with nortriptyline or escitalopram.

RESULTS

No baseline or longitudinal correlations between depression scores and serum levels of BDNF and VEGF were found, and the baseline serum levels did not predict the MADRS depression score after 12 weeks of treatment or the improvement in depression scores. Interestingly, we observed a significant baseline and longitudinal correlation between serum levels of BDNF and VEGF. The two classes of antidepressant treatment did not affect the results differently.

LIMITATIONS

Information on potential factors influencing the serum levels is missing.

CONCLUSION

Our results do not support the neurotrophic model of depression, since a significant decrease in serum BDNF and VEGF levels after 12 weeks of antidepressant treatment was observed. Our study encourages future studies with large sample sizes, more observations and a longer follow-up period.

Serum brain-derived neurotrophic factor levels in relation to comorbid depression and cytokine levels in Nepalese men with alcohol-use disorders

Neurodegenerative and inflammatory processes are involved separately in major depression (MD) and alcohol-use disorders (AUD). Little is known about the nature of this relationship in the context of comorbid AUD and depression disorders. In this study, we determined brain-derived neurotrophic factor (BDNF) serum levels in patients with AUD and tested whether BDNF levels were related to history of major depression, recent depressive symptoms, AUD severity, and TNF-α and IL-6 levels. Nepalese male AUD inpatients (N=152) abstinent from alcohol for an average of 34 days were administered structured interviews to assess depression symptoms and pattern and extent of alcohol use, and to generate research diagnoses for AUD and MD. AUD severity was assessed by scores on the Alcohol Use Disorder Identification Test. Serum BDNF and cytokines were measured using ELISA and multiplex technology, respectively. Although serum BDNF levels were unrelated to MD history, patients with recent depressive symptoms (n=42) had lower (mean±SD) BDNF serum levels compared to those without (n=110) (21.6±8.1 ng/mL vs. 26.0±9.6 ng/mL; p=0.010), and patients with higher AUD severity and binge-drinking patterns had higher mean serum BDNF levels compared to lower AUD severity and non-binging (25.9±9.7 ng/mL vs. 22.1±8.7 ng/mL; p=0.022 and 25.7±9.3 vs. 21.8±9.7 ng/mL; p=0.029, respectively). Positive correlations were present between BDNF and TNF-α (r=0.39, p<0.001) and IL-6 (r=0.2, p=0.027). In particular, TNF-α levels were predictive of BDNF levels after controlling for confounders (B=0.3 [95% CI=0.2-0.5], p<0.001). These findings show that in alcohol-using populations, peripheral BDNF levels are related to severity of AUD as well as presence of depressive symptoms. The significant associations between inflammatory and neurotrophic factors may have implications for neuroadaptive changes during recovery from AUD.

Apathy and APOE4 are associated with reduced BDNF levels in Alzheimer's disease

Reduced brain-derived neurotrophic factor (BDNF) signaling is considered as a pathogenic event in early Alzheimer's disease (AD), but the influence of apathy and apolipoprotein E ε4 allele (APOE4) on serum BDNF values was not previously investigated in AD. We evaluated serum BDNF levels in AD, amnestic mild cognitive impairment (MCI), and control subjects. Baseline BDNF levels were similar in AD, MCI, and controls. AD patients having apathy showed lower BDNF values than patients without apathy (p < 0.05). After correction for the influence of apathy, APOE4 carriers showed lower BDNF levels (p < 0.01) and MMSE scores (p < 0.01) than non-APOE4 carriers in the subgroup of AD females, but not in males. Significant (p < 0.05) positive correlations between BDNF values and MMSE scores were only observed in subgroups of AD males and of AD patients without apathy. These results are showing the association of apathy and APOE4 with reduced serum BDNF levels in AD, and are suggesting that BDNF reductions might contribute to the worse cognitive performance exhibited by AD apathetic patients and female APOE4 carriers.

Electroconvulsive therapy improves clinical manifestations of treatment-resistant depression without changing serum BDNF levels

Electroconvulsive therapy (ECT) is effective in treatment-resistant depression (TRD). It may act through intracellular process modulation, but its exact mechanism is still unknown. Animal research supports a neurotrophic effect for ECT. We aimed to investigate the association between changes in serum brain-derived neurotrophic factor (sBDNF) levels and clinical improvement following ECT in patients with TRD. Twenty-one patients with TRD (2 men, 19 women; mean age, 63.5 years; S.D., 11.9) were assessed through the Hamilton Depression Rating Scale (HDRS), the Brief Psychiatric Rating Scale (BPRS), and the Clinical Global Impressions scale, Severity (CGIs) before and after a complete ECT cycle. At the same time-points, patients underwent blood withdrawal for measuring sBDNF levels. ECT significantly reduced HDRS, BPRS, and CGIS scores, but not sBDNF levels. No significant correlation was found between sBDNF changes, and each of HDRS, BPRS, and CGIs score changes. sBDNF levels in TRD patients were low both at baseline and post-ECT. Our results do not support that improvements in TRD following ECT are mediated through increases in sBDNF levels.

Epigenetic alterations in depression and antidepressant treatment

Epigenetic modifications control chromatin structure and function, and thus mediate changes in gene expression, ultimately influencing protein levels. Recent research indicates that environmental events can induce epigenetic changes and, by this, contribute to long-term changes in neural circuits and endocrine systems associated with altered risk for stress-related psychiatric disorders such as major depression. In this review, we describe recent approaches investigating epigenetic modifications associated with altered risk for major depression or response to antidepressant drugs, both on the candidate gene levels as well as the genome-wide level. In this review we focus on DNA methylation, as this is the most investigated epigenetic change in depression research.

Improved Sleep Quality is Associated with Reductions in Depression and PTSD Arousal Symptoms and Increases in IGF-1 Concentrations

STUDY OBJECTIVES

One-third of deployed military personnel will be diagnosed with insomnia, placing them at high risk for comorbid depression, posttraumatic stress disorder (PTSD), and medical conditions. The disruption of trophic factors has been implicated in these comorbid conditions, which can impede postdeployment recovery. This study determined if improved sleep quality is associated with (1) reductions in depression and posttraumatic symptoms, as well as enrichments in health-related quality of life (HRQOL), and (2) changes in plasma concentrations of brain derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1).

METHODS

Forty-four military personnel diagnosed with insomnia underwent clinical evaluations and blood draws at pretreatment and at posttreatment following cognitive behavioral therapy for insomnia and automatic positive airway pressure treatment. Participants were classified as sleep improved (n = 28) or sleep declined (n = 16) based on their change in pretreatment to posttreatment Pittsburgh Sleep Quality Index (PSQI) score. Both groups were compared on outcomes of depression, PTSD, HRQOL, BDNF, and IGF-1.

RESULTS

Paired t-tests of the sleep improved group revealed significant declines in depression (p = 0.005) and posttraumatic arousal (p = 0.006) symptoms, and a significant increase in concentrations of IGF-1 (p = 0.009). The sleep declined group had no relevant change in psychiatric symptoms or trophic factors, and had further declines on five of eight dimensions of HRQOL. Between-group change score differences were significant at p < 0.05.

CONCLUSIONS

These findings suggest that interventions, which successfully improve sleep quality, are an effective means to reduce the depression and posttraumatic arousal symptoms common to military personnel, as well as increase protective trophic factors implicated in these conditions.

Blood BDNF level is gender specific in severe depression

Though the role of brain derived neurotrophic factor (BDNF) as a marker for major depressive disorder (MDD) and antidepressant efficacy has been widely studied, the role of BDNF in distinct groups of patients remains unclear. We evaluated the diagnostic value of BDNF as a marker of disease severity measured by HAM-D scores and antidepressants efficacy among MDD patients. Fifty-one patients who met DSM-IV criteria for MDD and were prescribed antidepressants and 38 controls participated in this study. BDNF in serum was measured at baseline, 1st, 2nd and 8th treatment weeks. Depression severity was evaluated using the Hamilton Rating Scale for Depression (HAM-D). BDNF polymorphism rs6265 (val66met) was genotyped. We found a positive correlation between blood BDNF levels and severity of depression only among untreated women with severe MDD (HAM-D>24). Serum BDNF levels were lower in untreated MDD patients compared to control group. Antidepressants increased serum BDNF levels and reduced between-group differences after two weeks of treatment. No correlations were observed between BDNF polymorphism, depression severity, duration of illness, age and BDNF serum levels. Further supporting the role of BDNF in the pathology and treatment of MDD, we suggest that it should not be used as a universal biomarker for diagnosis of MDD in the general population. However, it has diagnostic value for the assessment of disease progression and treatment efficacy in individual patients.

Chronic depression is associated with a pronounced decrease in serum brain-derived neurotrophic factor over time

One of the leading neurobiological hypotheses on depression states that decreased expression of brain-derived neurotrophic factor (BDNF) contributes to depression. This is supported by consistent findings of low serum BDNF levels in depressed patients compared with non-depressed controls. Whereas it has been generally assumed that this is a state characteristic of depression, strong inferences about state or trait effects require a longitudinal study design. To investigate the longitudinal association between serum BDNF and depression, we measured serum BDNF, (current and past) depression status, use of antidepressants, and all potential covariates at baseline and after 2 years in 1751 individuals, consisting of patients with an incident (n=153), remitted (n=420) and persistent depression (n=310) and non-depressed controls (n=868). We analyzed change/differences in serum BDNF across these four groups with analyses of covariance adjusted for covariates and baseline BDNF value, together with the effects of starting and stopping antidepressant treatment. Our analyses revealed a significant difference for the depression course groups (P=0.007). Compared with non-depressed controls, persistently depressed and remitted patients had a steeper decrease of BDNF levels over time (-1.33 (P=0.001) and -0.97 ng ml(-1) (P=0.011), respectively), whereas BDNF reductions in patients with incident depression were similar to those in healthy controls. Initiation or discontinuation of antidepressants was not associated with BDNF change (P=0.72). These findings suggest that BDNF not only contributes to depression, but that depression in turn may also contribute to low BDNF.

Brain-derived neurotrophic factor Val66Met polymorphism and 6-month antidepressant remission in depressed Caucasian patients

BACKGROUND

Whether the Brain Derived Neurotrophic Factor (BDNF) Val66Met polymorphism can predict antidepressant drug efficacy in depressed patients remains unclear, suggesting that it may depend on antidepressant classes. We assessed the impact of Val66Met polymorphism on antidepressant response and remission depending on antidepressant classes.

METHODS

In a 6-month prospective, real-world setting, treatment study, 345 Caucasian depressed patients requiring a new or different drug treatment with a selective serotonin reuptake inhibitor (SSRI), a serotonin and noradrenalin reuptake inhibitor (SNRI) or a tricyclic antidepressant (TCA), were genotyped and assessed for response and remission.

RESULTS

231 (67%) patients were homozygous for the Val66 allele (Val/Val) and 114 (33%) were carriers of Met allele (Met). 152 (44.1%) patients were treated with SSRI, the others with SNRI/TCA. Both response and remission were explained by interactions between the Val66Met polymorphism and antidepressant drug classes (multivariate models adjusted for propensity-scores: p=0.02 and p=0.03 respectively). With SSRI, Val/Val patients had a higher response rate 3 months post-treatment than Met patients (68.1% versus 44%; adjusted-OR: 3.04, IC95% [1.05; 9.37], p=0.04). With SNRI/TCA, Val/Val patients had a lower remission rate 6 months post-treatment than Met patients (33.3% versus 60.9%, adjusted-OR: 0.27, IC95% [0.09; 0.76], p=0.02).

LIMITATIONS

Limited sample size.

CONCLUSIONS

This study argues for a personalized prescription of antidepressants in Caucasian patients with major depressive disorder, based on the BDNF Val66Met polymorphism: SSRI should be preferred for Val/Val patients and SNRI/TCA for Met patients. Further studies are required to confirm these data.

BDNF serum levels are not related to cognitive functioning in older depressed patients and controls

BACKGROUND

Depression and cognitive decline are highly prevalent in older persons and both are associated with low serum brain derived neurotrophic factor (BDNF). Mutual pathways of depression and cognitive decline in older persons may explain the overlap in symptoms and low serum BDNF. We hypothesized that serum BDNF levels are lower in depressed elderly with poor cognitive performance (global or specifically in working memory, speed of information processing, and episodic memory) compared to depressed elderly without cognitive impairment or non-depressed controls.

METHODS

BDNF Serum levels and cognitive functioning were examined in 378 depressed persons and 132 non-depressed controls from a large prospective study on late-life depression. The association between BDNF levels and each cognitive domain among the depressed patients was tested by four separate linear regression models adjusted for relevant covariates. An analysis of covariance (ANCOVA) was performed to compare BDNF serum levels in three groups (depression with cognitive impairment, depression without cognitive impairment, and non-depressed controls), when adjusted for potential confounders.

RESULTS

No significant linear association was found between BDNF and any of the four cognitive domains tested. There are no differences in BDNF levels between controls and depressed patients with or without cognitive impairment global or in specific domains after controlling for confounders.

CONCLUSIONS

BDNF serum levels in this cohort of older depressed patients and controls are not related to cognitive functioning. As BDNF is essential for the survival and functioning of neurons, its levels may remain normal in stages of disease where remission is achievable.

Association between smoking, nicotine dependence, and BDNF Val66Met polymorphism with BDNF concentrations in serum

INTRODUCTION

Nicotine use is associated with the upregulation of brain-derived neurotrophic factor (BDNF) in serum. An association between smoking and the BDNF Val(66)Met polymorphism has also been found. The aim of this study is to examine the levels of serum BDNF in never-smokers, former smokers, and current smokers-with and without nicotine dependence-and to examine the interaction of the polymorphism and smoking status with serum BDNF.

METHODS

We used baseline serum and gene data of BDNF on 2,088 participants from the Netherlands Study of Depression and Anxiety (NESDA) to investigate smoking-BDNF association while controlling for potential confounding variables. Nicotine dependence was assessed with the Fagerstrom Test for Nicotine Dependence (FTND).

RESULTS

Smokers with and without nicotine dependence had higher levels of serum BDNF than former and never-smokers. Nicotine dependence and number of cigarettes smoked per day did not add to the prediction of serum BDNF; however, total number of smoking years was a significant predictor of serum BDNF. There was no association of BDNF Val(66)Met, nor an interaction of this polymorphism and smoking status, with serum BDNF.

CONCLUSIONS

Current smoking and higher number of smoking years are associated with higher levels of serum BDNF, and this is independent of the BDNF genotype. Nicotine dependence itself is not associated with a further increase or decrease of serum BDNF. Longitudinal investigations that address changes in serum BDNF in incident smokers and/or in quitters may be useful to understand the association of smoking with BDNF.

Involvement of norepinephrine and serotonin system in antidepressant-like effects of hederagenin in the rat model of unpredictable chronic mild stress-induced depression

CONTEXT

Previous studies from our laboratory indicated that both acute and subchronic administration of Fructus Akebiae (FAE) [the fruit of Akebiae quinata (Thunb.) Decne, (Lardizabalaceae)] produce antidepressant-like effects in animal depressive behavior tests. FAE contains approximately 70% of hederagenin (HG) as its main chemical component.

OBJECTIVE

This study compared the antidepressant ability of FAE with that of HG in mice and further investigated the antidepressant-like effects and potential mechanisms of HG in rats subjected to unpredictable chronic mild stress (UCMS).

MATERIALS AND METHODS

Mice received FAE (50 mg/kg) and HG (20 mg/kg) once a day via intragastric administration (i.g.) for 3 weeks. The anxiolytic and antidepressant activities of FAE and HG were compared using elevated plus maze (EPM) and behavioral despair tests including tail suspension test (TST) and forced swimming test (FST), respectively. Antidepressant effects of HG (5 mg/kg) were assessed using the UCMS depressive rat model. Moreover, the levels of monoamine neurotransmitters and relevant gene expression in UCMS rats' hippocampi were determined through high-performance liquid chromatography with electrochemical detection and real-time polymerase chain reaction techniques.

RESULTS

The results of our preliminary screening test suggest that HG at 20 mg/kg, while not FAE at 50 mg/kg, significantly decreased the immobility in both TST and FST compared with the vehicle group when administered chronically; however, there were no significant differences observed between the HG and the FAE group. Chronic administration of HG failed to significantly reverse the altered crossing and rearing behavioral performance, time spent in the open arm and closed entries in the EPM, even if they showed an increased tendency, but HG significantly increased the percent of sucrose preference in the sucrose preference test (SPT) and decreased the immobility time in the FST. HG showed that significant increases of norepinephrine and serotonin levels and exhibited a tendency to increase the expression of 5-hydroxytryptamine (serotonin) 1A receptor mRNA, and to significantly decrease the expression of the mRNA for the serotonin transporter (5-HTT). However, there were no significant differences in the expression of the brain-derived neurotrophic factor.

CONCLUSION

These findings confirm the antidepressant-like effects of HG in a behavioral despair test and UCMS rat model, which may be associated with monoamine neurotransmitters and 5-HTT mRNA expression.

New insights into the neurobiological mechanisms of major depressive disorders

OBJECTIVE

To review the current evidence about the neurobiological mechanisms in major depressive disorders (MDD) and the key findings from studies using neuroimaging tools and animal models.

METHOD

This paper gives an overview of the role of genetic and environmental factors in the pathophysiology of MDD and describes the structural changes in brain structures of depressed individuals. A closer look is given at the molecular processes and neurotransmitters implicated in this mental disorder. Moreover, this paper discusses key findings from recent research using animal models and their relevance for clinical applications.

RESULTS

Although the exact cause of MDD is not known, there is enough evidence showing that genetic, psychological and environmental factors significantly increase the risk of developing this disease. Individuals affected by MDD exhibit a reduced volume of structures such as the amygdala, hippocampus and basal ganglia, as well as altered level of neurotransmitters in the brain.

CONCLUSION

The studies presented in this review show promising results that could shed light on the molecular mechanisms of MDD. However, more work needs to be done to better understand this psychiatric disorder and promote the development of new treatment strategies.

Nutritional medicine as mainstream in psychiatry

Psychiatry is at an important juncture, with the current pharmacologically focused model having achieved modest benefits in addressing the burden of poor mental health worldwide. Although the determinants of mental health are complex, the emerging and compelling evidence for nutrition as a crucial factor in the high prevalence and incidence of mental disorders suggests that diet is as important to psychiatry as it is to cardiology, endocrinology, and gastroenterology. Evidence is steadily growing for the relation between dietary quality (and potential nutritional deficiencies) and mental health, and for the select use of nutrient-based supplements to address deficiencies, or as monotherapies or augmentation therapies. We present a viewpoint from an international collaboration of academics (members of the International Society for Nutritional Psychiatry Research), in which we provide a context and overview of the current evidence in this emerging field of research, and discuss the future direction. We advocate recognition of diet and nutrition as central determinants of both physical and mental health.

Changes in brain-derived neurotrophic factor (BDNF) during abstinence could be associated with relapse in cocaine-dependent patients

Brain-derived neurotrophic factor (BDNF) is involved in cocaine craving in humans and drug seeking in rodents. Based on this, the aim of this study was to explore the possible role of serum BDNF in cocaine relapse in abstinent addicts. Forty cocaine dependent subjects (DSM-IV criteria) were included in an inpatient 2 weeks abstinence program. Organic and psychiatric co-morbidities were excluded. Two serum samples were collected for each subject at baseline and at after 14 abstinence days. After discharge, all cocaine addicts underwent a 22 weeks follow-up, after which they were classified into early relapsers (ER) (resumed during the first 14 days after discharge,) or late relapsers (LR) (resumed beyond 14 days after discharge). The only clinical differences between groups were the number of consumption days during the last month before detoxification. Serum BDNF levels increased significantly across the 12 days of abstinence in the LR group (p=0.02), whereas in the ER group BDNF remained unchanged. In the ER group, the change of serum BDNF during abstinence negatively correlated with the improvement in depressive symptoms (p=0.02). These results suggest that BDNF has a role in relapse to cocaine consumption in abstinent addicts, although the underlying neurobiological mechanisms remain to be clarified.

Brain-derived neurotrophic factor and subcallosal deep brain stimulation for refractory depression

OBJECTIVES

Subcallosal cingulate (SCC) deep brain stimulation (DBS) is a promising experimental treatment for treatment-resistant depression (TRD). Given the role of brain-derived neurotrophic factor (BDNF) in neuroplasticity and antidepressant efficacy, we examined the effect of SCC-DBS on serum BDNF in TRD.

METHODS

Four patients with TRD underwent SCC-DBS treatment. Following a double-blind stimulus optimization phase of 3 months, patients received continuous stimulation in an open label fashion for 6 months. Clinical improvement in depressive symptoms was evaluated bi-weekly for 6 months using the Hamilton Depression Rating Scale (HDRS). Mature serum BDNF levels were measured before and 9-12 months after surgery.

RESULTS

Three patients responded to SCC-DBS: two showed full clinical response (50% reduction in HDRS scores) and one had partial response (35% reduction in HDRS scores) at the clinical endpoint. Interestingly, all four patients showed reduction in serum BDNF concentration from pre-DBS baseline.

CONCLUSIONS

SCC-DBS for TRD may be associated with decreased levels of serum BDNF. Longitudinal studies with multiple measurements in a larger sample are required to determine the role of BDNF as a biomarker of SCC-DBS antidepressant efficacy.

Decreased serum levels of polyunsaturated fatty acids and folate, but not brain-derived neurotrophic factor, in childhood and adolescent females with depression

Evidence from observational studies suggests that there is an association among depression and brain-derived neurotrophic factor (BDNF), polyunsaturated fatty acids (PUFAs), and folate; however, this association has yet to be examined in childhood and adolescent depression. The objective was to determine whether the BDNF, PUFAs, and folate in serum differ between first-episode childhood and adolescent depressed patients and healthy controls. We measured the serum levels of BDNF, PUFAs, and folate of cases admitted to the hospital for depression (n=24) and compared it to that of controls (n=26). Subjects and their parents were informed about the nature and the purpose of this study, and a consent form was signed by parents. The ethics committee of Hirosaki University Graduate School of Medicine approved the study protocol. There were significant differences in the docosahexanoic acid (DHA), arachidonic acid (AA), and folate levels between cases and controls. Serum levels of DHA, AA, and folate levels in the patients group were statistically lower than those in the control group, while serum levels of BDNF were not different between cases and controls. These results are in line with findings of previous studies involving adult and elderly subjects, demonstrating lower levels of PUFAs and folate in patients with depression than healthy controls. However, further studies using larger sample size are warranted.

Serum brain-derived neurotrophic factor level in elderly women depression: a community-based study

OBJECTIVES

Serum levels of brain-derived neurotrophic factor (BDNF) have been shown to be lower in patients with major depressive disorder (MDD) than in healthy persons. Although several studies have examined the associations between serum BDNF levels and broader categories of depression identified by psychiatrists or depressive symptoms measured with depression scales among nonpatient populations, some of these studies did not consider possible confounders and included mostly young or middle-aged subjects and nonrepresentative control subjects, such as volunteers and patients' relatives. Therefore, it remains unclear that whether MDD, broader categories of depression, or depressive symptoms in the elderly are associated with BDNF. The present study examined these associations in a community sample and controlled for confounders.

METHODS

The subjects were 538 women aged 78 to 88 years who had participated in a follow-up survey of a cohort and had scored 24 or more on the Mini-Mental State Examination. Two depression scales were administered, and, using the Structured Clinical Interview for DSM-IV, psychiatrists identified 53 persons having any mood disorder (AMD) - 8 with MDD and 45 with other types of depression according to the DSM-IV or its research criteria - and 106 healthy controls.

RESULTS

Subjects with MDD had serum BDNF levels lower than did controls but subjects with AMD did not. The severity of depressive symptoms assessed with either of the 2 depression scales was negatively correlated with serum BDNF levels in all subjects and in subjects remaining after persons with MDD or AMD were excluded. These associations were significant after controlling for possible confounders.

CONCLUSION

We have found an association between MDD and serum BDNF levels in old-old women, as has previously been found in younger patients. Although serum BDNF levels were not found to be associated with the broader category of depression, they were associated with depressive symptoms among subjects without clinical depression.

Treatment-resistant Late-life Depression: Challenges and Perspectives

The current Review article provides a narrative review about the neurobiological underpinnings and treatment of treatment resistant late-life depression (TRLLD). The manuscript focuses on therapeutic targets of late-life depression, which include pharmacological, psychological, biophysical and exercise treatment approaches. Therefore, we summarize available evidences on that kind of therapies for patients suffering from late-life depression. The search for evidences of therapeutic options of late-life depression were done using searching websites as "pubmed", and using the searching terms "depression", "late-life depression", "treatment", "biophysical therapy", "exercise therapy", "pharmacological therapy" and "psychological therapy". To the end, we summarize and discuss current data, providing some directions for further research. Treatment recommendations for elderly depressive patients favour a multimodal approach, containing psychological, pharmacological and secondary biophysical therapeutic options. Particularly, a combination of psychotherapy and antidepressant medication reflects the best therapeutic option. However, mostly accepted and used is the pharmacological treatment although evidence suggests that the drug therapy is not as effective as it is in younger depressive patients. Further studies employing larger samples and longer follow-up periods are necessary and may focus on comparability of study designs and involve novel approaches to establish the validity and reliability of multimodal treatment programs.

Mineralocorticoid receptor genotype moderates the association between physical neglect and serum BDNF

The objective of this study is to investigate if a polymorphism in the NR3C2 gene moderates the association between childhood trauma on serum levels of brain derived neurothrophic factor (sBDNF). sBDNF was used here as a general marker of alteration in brain function. This is a community cross sectional study comprising 90 adolescents (54 with anxiety disorders). DNA was extracted from saliva in order to genotype the MR-2G/C (rs2070951) polymorphism using real time PCR. Blood was collected for sBDNF Elisa immunoassay. The Childhood Trauma Questionnaire (CTQ) was used to evaluate childhood abuse and neglect. Main effects and gene environment interactions were tested using linear regression models. Anxiety disorders were not associated with the MR-2G/C polymorphism or with sBDNF levels, but the number of C alleles of the MR-2G/C polymorphism was significantly associated with higher sBDNF levels (b = 8.008; p-value = 0.001). Subjects with intermediate and high exposure to physical neglect showed higher sBDNF levels if compared to subjects non-exposed (b = 11.955; p = 0.004 and b = 16.186; p = 0.009, respectively). In addition, we detected a significant physical neglect by MR-2G/C C allele interaction on sBDNF levels (p = 0.005), meaning that intermediate and high exposure to childhood neglect were only associated with increased sBDNF levels in subjects with the CC genotype, but not in subjects with other genotypes. Our findings suggest that genetic variants in NR3C2 gene may partially explain plastic brain vulnerability to traumatic events. Further studies are needed to investigate the moderating effects of NR3C2 gene in more specific markers of alteration in brain function.

Fast BDNF serum level increase and diurnal BDNF oscillations are associated with therapeutic response after partial sleep deprivation

OBJECTIVE

Preclinical and clinical studies support a role for brain-derived neurotrophic factor (BDNF) in the pathophysiology of stress-related mood disorders. Furthermore, BDNF seems to be linked to antidepressant action. Available pharmacological treatments for depression are characterized by significant limitations with low efficacy and a major delay until treatment response. This demonstrates the urgent need for more efficient and fast-acting antidepressants. Besides ketamine, sleep deprivation (SD) as well as partial sleep deprivation (PSD) are effective and fast-acting antidepressant methods. However, the underlying molecular mechanisms of SD are not well understood; especially possible mechanisms explaining the rapid, but transient antidepressant effect of SD are unknown.

METHODS

We evaluated serum BDNF from 28 patients suffering from major depressive disorder (MDD), who were naïve to SD therapy at seven different time points within a 32 h time window before (day 0) and after PSD (day 1). PSD-response was assessed by 6-Items of the Hamilton Depression Rating Scale (HDRS) before (day 0) and at follow-up after 2 weeks (FU2).

RESULTS

PSD induced a very fast increase in BDNF serum levels at day 1 which parallels clinical findings, since levels increased with decreasing depression scores in all participants. Notably, responders showed a significant diurnal BDNF serum variation not only after PSD but already before PSD treatment, while diurnal profile of serum BDNF from non-responders did not vary.

CONCLUSIONS

The elasticity in diurnal serum BDNF variation is associated with favourable treatment response to PSD in patients suffering from MDD. Therefore, a normalized BDNF serum profile which oscillates in a circadian fashion seems to precede, rather than follow a favourable treatment outcome in depressed patients. Furthermore the fast increase of BDNF is comparable to effects seen with ketamine infusion.

Brain-derived neurotrophic factor as a suicide factor in mental disorders

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) plays a critical role in brain plasticity processes and serum levels have been demonstrated to be altered in patients with different mental disorder including suicidal behaviour. The objective of this study was to examine the association between serum BDNF levels as a possible peripheral indicator of suicide behaviour in subjects suffering from depression, personality disorders (PDs) and adjustment disorders (ADs) with or without suicide attempt.

METHODS

The research included 172 randomly selected individuals suffering from recurrent depressive disorder (RDD; F 33.2), emotionally unstable PD (F 60.3) and AD (F 43.2), with or without attempted suicide according to the criteria of the ICD-10 (International Statistical Classification of Diseases and Related Health Problems 10th Revision) and 60 phenotypically health control subjects. In the group of patients, 73% subjects took some form of psychopharmacotherapy. Serum BDNF levels were measured by enzyme linked immunosorbent assay.

RESULTS

Subjects with PD and AD with suicide attempts had significantly lower serum BDNF levels than those without suicide attempts. In groups of subjects with PD and AD, those taking psychopharmacotherapy had higher serum BDNF levels. In the group of subjects with RDD, there were no differences with respect to suicide attempts or psychopharmacotherapy. Logistical regression analysis was indicated that psychopharmacotherapy and serum BDNF levels statistically correlated with suicide attempts.

CONCLUSION

The lower levels of BDNF in subjects suffering from PD and AD with suicide attempts, suggest that the serum BDNF level is a potential marker of suicidal behaviour, independent of mental disorders.

Electroconvulsive therapy improves clinical manifestation with plasma BDNF levels unchanged in treatment-resistant depression patients

Electroconvulsive therapy (ECT) is the most effective treatment in treatment-resistant depression; it may modulate intracellular processes in such patients. This study aimed to investigate the association between changes in plasma brain-derived neurotrophic factor (BDNF) levels and the clinical improvements after ECT for patients with treatment-resistant depression. Fifty-five inpatients with treatment-resistant depression were recruited. The severity of depression was measured using the 17-item Hamilton Rating Scale for Depression (HAMD-17) and the Clinical Global Impression-Severity (CGI-S) before ECT, after every 3 sessions of ECT, and at the end of ECT. Plasma BDNF levels were measured in all subjects before and after ECT. The severity of depression was significantly reduced on the HAMD-17 (p < 0.001) and the CGI-S (p < 0.001) after the end of ECT. There were no significant differences in plasma BDNF levels after ECT (p = 0.615). No significant correlation was found between changes in plasma BDNF levels and changes in HAMD-17 scores (r = 0.188, p = 0.169). Our results do not support the hypothesis that improvements in treatment-resistant depression patients after ECT are due to changes in BDNF levels.

Serum brain-derived neurotrophic factor and cognitive functioning in underweight, weight-recovered and partially weight-recovered females with anorexia nervosa

Several studies support the assumption that the brain-derived neurotrophic factor (BDNF) plays an important role in the pathophysiology of eating disorders. In the present cross-sectional and longitudinal study, we investigated BDNF levels in patients with anorexia nervosa (AN) at different stages of their illness and the association with cognitive functioning. We measured serum BDNF in 72 acutely underweight female AN patients (acAN), 23 female AN patients who successfully recovered from their illness (recAN), and 52 healthy control women (HCW). Longitudinally, 30 acAN patients were reassessed after short-term weight gain. The association between BDNF levels and psychomotor speed was investigated using the Trail Making Test. BDNF serum concentrations were significantly higher in recAN participants if compared to acAN patients and increased with short-term weight gain. In acAN patients, but not HCW, BDNF levels were inversely associated with psychomotor speed. AcAN patients with higher BDNF levels also had lower life time body mass indexes. Taken together, our results indicate that serum BDNF levels in patients with AN vary with the stage of illness. Based on the pleiotropic functions of BDNF, changing levels of this neurotrophin may have different context-dependent effects, one of which may be the modulation of cognitive functioning in acutely underweight patients.

The effects of exercise on oxidative stress (TBARS) and BDNF in severely depressed inpatients

Exercise can be an effective treatment for depression. Although the efficacy of exercise is well established, little is known concerning the biological changes associated with the antidepressant effects of exercise. A randomized, controlled trial was conducted to evaluate the effects of adding exercise to the usual treatment on the thiobarbituric acid-reactive substances (TBARS) and brain-derived neurotrophic factor (BDNF) serum levels of severely depressed inpatients. Twenty-six participants were randomized to an exercise group (n=15, exercise+treatment as usual) or a control group (n=11, treatment as usual). The participants in the exercise group completed a targeted dose of 16.5 kcal/kg/week of aerobic exercise, three times per week, throughout their hospitalizations. The control group did not exercise during their hospitalizations. The mean hospitalization length was of 21.63 (4.5)×23.82 (5.7) days for exercise and control groups, respectively. The exercise group performed a median of nine sessions. After adjusting for previous tobacco use, a significant group×time interaction was found for TBARS serum levels (p=0.02). A post hoc Bonferroni test revealed differences between the exercise and control groups at discharge. A significant time effect (p<0.001) but no group×time interaction was found (p=0.13) for BDNF serum levels. Adding exercise to the usual treatment of severely depressed inpatients decreases the TBARS serum levels of severely depressed inpatients after 3 weeks. Adding exercise had no additional effects on BDNF serum levels.

RETRACTED: Electroconvulsive therapy and aerobic exercise training increased BDNF and ameliorated depressive symptoms in patients suffering from treatment-resistant major depressive disorder

BACKGROUND

To treat patients suffering from treatment-resistant major depressive disorder (TR-MDD), research has focused on electroconvulsive therapy (ECT) and aerobic exercise training (AET). Brain derived neurotrophic factor (BDNF) seems to be key in MDD. The aims of the present study were therefore two-fold, to investigate in a three-arm interventional study the differential effects of ECT, ECT plus AET, and AET alone in patients suffering from TR-MDD on 1. depressive symptoms and 2.

BDNF METHODS

60 patients with TR-MDD (mean age: 31 years; 31.6% female patients) were randomly assigned either to the ECT, ECT + AET, or AET condition. The AET condition consisted of treadmill exercise for 30 min, three times a week. Both depression severity and BDNF levels were assessed at baseline and 4 weeks later. All patients were further treated with an SSRI standard medication.

RESULTS

BDNF levels increased over time in all three study conditions. After completion of the intervention program, the ECT group showed significantly higher BDNF levels compared to the ECT + AET and the AET conditions. Depressive symptoms decreased in all three conditions over time. The combination of ECT + AET led to a significantly greater decrease than in either the ECT or AET alone conditions. BDNF levels were not associated with symptoms of depression.

CONCLUSIONS

The pattern of results suggests that ECT, AET and particularly their combination are promising directions for treatment patients suffering from TR-MDD, and that it remains unclear to what extent BDNF is key and a reliable biomarker for TR-MDD.

Serum Brain-derived neurotrophic factor levels in post-stroke depression

BACKGROUND

Depression is a frequent mood disorder that affects around a third of stroke patients and has been associated with poorer outcome. Our aim was to determine whether there is a relationship between serum Brain-derived neurotrophic factor (BDNF) levels and post-stroke depression (PSD).

METHODS

Two hundred and sixteen ischemic stroke patients admitted to the hospital within the first 24h after stroke onset were consecutively recruited and followed up for 3 months. Based on the symptoms, diagnoses of depression were made in accordance with DSM-IV criteria for post-stroke depression at day 90. Enzyme-linked immunosorbent assay (ELISA) was used to measure serum levels of BDNF at admission. Multivariate analyses were performed using logistic regression models.

RESULTS

In our study, 59 patients (27.3%) were diagnosed as having major depression at 3 months. Patients with major depression showed lower levels of serum BDNF [8.1 (5.6-9.4) vs. 13.7 (10.4-16.5)ng/ml, P<0.0001] at admission. In multivariate analyses, serum BDNF was an independent predictor of PSD at 3 months [odds ratio (OR): 0.79(0.72-0.87), P=0.003]. Serum levels of BDNF≤10.2ng/ml were independently associated with post-stroke (OR, 11.5; 95% CI, 5.6-23.4, P<0.0001), after adjustment for possible variables.

CONCLUSION

The present study demonstrates a strong relationship between serum BDNF levels at admission and the development of PSD within 3 months. Further studies are necessary to confirm this association, which may open the way to the proposal of new therapeutic options.

Brain-derived neurotrophic factor (BDNF)-epigenetic regulation in unipolar and bipolar affective disorder

BACKGROUND

Alterations of brain-derived neurotrophic factor (BDNF) DNA methylation at specific BDNF promoters and corresponding gene expressions are associated with pathology and the response to antidepressant (AD) therapy in affective disorders such as major depressive disorder (MDD) and bipolar disorder (BD).

METHODS

Genomic DNA was derived from peripheral blood mononuclear cells (PBMCs) and was bisulfite converted. Percentage of methylated reference (PMR) was calculated based on results from quantitative real-time PCR following the MethyLight protocol. For statistical analysis parametric procedures were performed as appropriate.

RESULTS

In this study 544 subjects were included, 207 MDD subjects, 59 BD subjects and 278 control subjects. The BDNF exon I promoter methylation resulted to be significantly increased in MDD subjects compared to BD subjects (p=0.0089) and control subjects (p<0.001). Furthermore, the increase of methylation in MDD subjects was significantly associated with AD therapy (p=0.0019) but not to the clinical features of depression such as the severity of symptoms (p=n.s.). None of the 12 investigated single nucleotide polymorphisms (SNP) showed significant genotype-methylation interactions.

LIMITATIONS

Although based on previous findings, the DNA methylation was evaluated within only one CpG island of the different alternative BDNF gene transcripts.

CONCLUSIONS

The results suggest that the methylation status might not only be affected by the disease phenotype but might also be further influenced by pharmacological treatment, therefore harbouring the possibility of identifying new insights for treatment options.

Low serum BDNF levels in depressed patients cannot be attributed to individual depressive symptoms or symptom cluster

OBJECTIVES

Low serum BDNF levels have been found in depressed patients. No study has systematically investigated whether individual symptoms or symptom profiles within a depressed population contribute to low BDNF levels found in depressed subjects.

METHODS

All 1070 patients with a past 6-month diagnosis of major depressive disorder from the Netherlands Study of Depression and Anxiety (NESDA) were included. Composite International Diagnostic Interview (CIDI) and Inventory of Depressive Symptoms (IDS) items were tested individually in separate multiple regression analyses with serum BDNF level as the dependent and the CIDI or IDS item as independent variable. Subsequently, we compared BDNF levels between patients with seasonal affective disorder (based on the Seasonal Pattern Assessment Questionnaire) and melancholic depression, atypical depression and moderate depression (based on a latent class analysis). All analyses were adjusted for confounders.

RESULTS

Only one item was significantly associated with serum BDNF levels, namely the CIDI item "loss of interest" (β = 0.14; P < 0.01). Counterintuitively the presence of this symptom was associated with higher BDNF levels. Other items and the comparison between different types of depression did not reveal significant differences.

CONCLUSIONS

Decreased serum BDNF levels in depression cannot be attributed to a specific symptom or symptom cluster.

Epigenetic alterations in depression and antidepressant treatment

Epigenetic modifications control chromatin structure and function, and thus mediate changes in gene expression, ultimately influencing protein levels. Recent research indicates that environmental events can induce epigenetic changes and, by this, contribute to long-term changes in neural circuits and endocrine systems associated with altered risk for stress-related psychiatric disorders such as major depression. In this review, we describe recent approaches investigating epigenetic modifications associated with altered risk for major depression or response to antidepressant drugs, both on the candidate gene levels as well as the genome-wide level. In this review we focus on DNA methylation, as this is the most investigated epigenetic change in depression research.

Cellular aging in depression: Permanent imprint or reversible process?: An overview of the current evidence, mechanistic pathways, and targets for interventions

Depression might be associated with accelerated cellular aging. However, does this result in an irreversible state or is the body able to slow down or recover from such a process? Telomeres are DNA-protein complexes that protect the ends of chromosomes and generally shorten with age; and therefore index cellular aging. The majority of studies indicate that persons with depression have shorter leukocyte telomeres than similarly aged non-depressed persons, which may contribute to the observed unfavorable somatic health outcomes in the depressed population. Some small-scale preliminary studies raise the possibility that behavioral or pharmacological interventions may either slow down or else reverse this accelerated telomere shortening, possibly through increasing the activity of the telomere-lengthening enzyme telomerase. This paper covers the current state of evidence in the relationship between depression and the telomere-telomerase system and debates whether depression-related cellular aging should be considered a reversible process or permanent damage.

The role of serotonin in adult hippocampal neurogenesis

Serotonin is probably best known for its role in conveying a sense of contentedness and happiness. It is one of the most unique and pharmacologically complex monoamines in both the peripheral and central nervous system (CNS). Serotonin has become in focus of interest for the treatment of depression with multiple serotonin-mimetic and modulators of adult neurogenesis used clinically. Here we will take a broad view of serotonin from development to its physiological role as a neurotransmitter and its contribution to homeostasis of the adult rodent hippocampus. This chapter reflects the most significant findings on cellular and molecular mechanisms from neuroscientists in the field over the last two decades. We illustrate the action of serotonin by highlighting basic receptor targeting studies, and how receptors impact brain function. We give an overview of recent genetically modified mouse models that differ in serotonin availability and focus on the role of the monoamine in antidepressant response. We conclude with a synthesis of the most recent data surrounding the role of serotonin in activity and hippocampal neurogenesis. This synopsis sheds light on the mechanisms and potential therapeutic model by which serotonin plays a critical role in the maintenance of mood.

Changes in serum levels of brain derived neurotrophic factor and nerve growth factor-beta in schizophrenic patients before and after treatment

Schizophrenia is one of the most debilitating diseases among psychiatric disorders. Recent studies suggest the existence of effective immunological changes in the pathophysiology of this disease. The purpose of the current study was to determine the changes in serum levels of Brain Derived Neurotrophic Factor (BDNF) and Nerve Growth Factor-beta (NGF) in schizophrenic patients before treatment and 40 days after treatment. In this case-control study, serum levels of BDNF and NGF were measured by ELISA in 26 patients with schizophrenia and 26 healthy controls. All patients were treated with clozapine or risperidone for 40 days. A positive and negative syndrome scale (PANSS) questionnaire has been used to recognize the severity of the disease and to assess the response to treatment. Neurotrophin concentrations were compared before and after the treatment and with control groups using paired t-test and ANOVA test. BDNF and NGF levels in the case group were more than levels after treatment, but these differences were significant only for NGF. Concentrations in both neurotrophins were higher than the control group. The statistically significant difference was observed between changes in the NGF levels in the case and the control group, while no significant difference was seen in changes of BDNF. The main conclusion to be drawn from this study was that the increase in BDNF and particularly NGF may have an important role in causing schizophrenia. And possibly drugs clozapine and risperidone help to treat the disease by reducing the concentration of Neurotrophins.

Major depressive disorder and accelerated cellular aging: results from a large psychiatric cohort study

Patients with major depressive disorder (MDD) have an increased onset risk of aging-related somatic diseases such as heart disease, diabetes, obesity and cancer. This suggests mechanisms of accelerated biological aging among the depressed, which can be indicated by a shorter length of telomeres. We examine whether MDD is associated with accelerated biological aging, and whether depression characteristics such as severity, duration, and psychoactive medication do further impact on biological aging. Data are from the Netherlands Study of Depression and Anxiety, including 1095 current MDD patients, 802 remitted MDD patients and 510 control subjects. Telomere length (TL) was assessed as the telomere sequence copy number (T) compared to a single-copy gene copy number (S) using quantitative polymerase chain reaction. This resulted in a T/S ratio and was converted to base pairs (bp). MDD diagnosis and MDD characteristics were determined by self-report questionnaires and structured psychiatric interviews. Compared with control subjects (mean bp=5541), sociodemographic-adjusted TL was shorter among remitted MDD patients (mean bp=5459; P=0.014) and current MDD patients (mean bp=5461; P=0.012). Adjustment for health and lifestyle variables did not reduce the associations. Within the current MDD patients, separate analyses showed that both higher depression severity (P<0.01) and longer symptom duration in the past 4 years (P=0.01) were associated with shorter TL. Our results demonstrate that depressed patients show accelerated cellular aging according to a 'dose-response' gradient: those with the most severe and chronic MDD showed the shortest TL. We also confirmed the imprint of past exposure to depression, as those with remitted MDD had shorter TL than controls.

Serum BDNF concentrations as peripheral manifestations of depression: evidence from a systematic review and meta-analyses on 179 associations (N=9484)

Meta-analyses, published in 2008-2010, have confirmed abnormally low serum brain-derived neurotrophic factor (BDNF) concentrations in depressed patients and normalization of this by antidepressant treatment. These findings are believed to reflect peripheral manifestations of the neurotrophin hypothesis, which states that depression is secondary to an altered expression of BDNF in the brain. Since the publication of these meta-analyses, the field has seen a huge increase in studies on these topics. This motivated us to update the evidence on the aforementioned associations and, in addition, to compile the data on serum BDNF concentrations in relation to the symptom severity of depression. Using a manifold of data as compared with earlier meta-analyses, we find low serum BDNF concentrations in 2384 antidepressant-free depressed patients relative to 2982 healthy controls and to 1249 antidepressant-treated depressed patients (Cohen's d=-0.71 and -0.56, P-values <0.0000001). When publication bias is accounted for, these effect-sizes become substantially smaller (d=-0.47 and -0.34, respectively, P-values<0.0001). We detect between-study heterogeneity in outcomes for which only year of publication and sample size are significant moderators, with more recent papers and larger samples sizes in general being associated with smaller between-group differences. Finally, the aggregated data negate consistent associations between serum BDNF concentrations and the symptom severity of depression. Our findings corroborate the claim that altered serum BDNF concentrations are peripheral manifestations of depression. However, here we highlight that the evidence for this claim is slimmer as was initially thought and amidst a lot of noise.

Val66Met polymorphism and serum brain-derived neurotrophic factor in bipolar disorder: an open-label trial

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) is consistently associated with acute mood episodes in bipolar disorder, but there is a lack of longitudinal data to support this hypothesis. In this 16-week open-label clinical trial, we tested the predictive role of BDNF Val66Met polymorphism on serum BDNF levels and the relationship of serum BDNF and clinical response in people with bipolar disorder during an acute illness episode.

METHOD

Sixty-four people with bipolar disorder who were medication-free at baseline and in an acute mood episode were recruited. They were matched with 64 healthy controls. Clinical evaluation, serum BDNF, and BDNF Val66Met polymorphism were determined at baseline, and change in serum BDNF was assessed in patients at weeks 2, 4, 8 and 16.

RESULTS

There were no differences between patients and controls in serum BDNF or in frequencies of the BDNF Val66Met polymorphism genotype at baseline. The multivariable model showed that Met carriers had a significantly different change in BDNF levels compared with Val homozygotes. Not achieving a complete remission was also associated with lower prospectively assessed BDNF levels.

CONCLUSION

This study provides the first longitudinal evidence that both the BDNF Val66Met polymorphism and remission status predict change in circulating BDNF levels.

BDNF in late-life depression: effect of SSRI usage and interaction with childhood abuse

Brain-Derived Neurotrophic Factor (BDNF) serum levels are abnormally low in depressed patients as compared to healthy controls and normalize with SSRI treatment. The aim of this study is to examine serum BDNF levels in late-life depression, stratified for SSRI usage, and to explore the relation between BDNF levels and specific depression characteristics as well as between BDNF levels and early and recent life stressors in late-life depression. We assessed serum BDNF levels in 259 depressed patients not using an SSRI, 99 depressed patients using an SSRI and 119 non-depressed controls (age range 60-93 years). Depressive disorders were diagnosed with the Composite International Diagnostic Interview (CIDI, version 2.1). Serum BDNF levels were significantly higher in depressed patients who used an SSRI compared to depressed patients not using SSRIs and compared to non-depressed controls, when adjusted for age, sex, life style characteristics, cognitive functioning and somatic comorbidity. Recent life-events, assessed with the List of Threatening Events-Questionnaire, were significantly associated with lower BDNF levels in non-depressed subjects only. Although a summary score of early traumatization (before the age of 16 years) was not associated with serum BDNF levels in any of the three groups, we found an interaction between a history of severe physical abuse and SSRI usage in the depressed group. Interestingly, higher serum levels of BDNF in depressed patients using SSRIs were only found in those patients without a history of severe childhood abuse and not in those with a history of severe childhood abuse.

A large, cross-sectional observational study of serum BDNF, cognitive function, and mild cognitive impairment in the elderly

Objective: The clinical relationship between brain-derived neurotrophic factor (BDNF) and cognitive function or mild cognitive impairment (MCI) is not well-understood. The purpose of this study was to identify the relationship between serum BDNF and cognitive function and MCI, and determine whether serum BDNF level might be a useful biomarker for assessing risk for MCI in older people.

Materials and Methods: A total of 4463 individuals aged 65 years or older (mean age 72 years) participating in the study. We measured performance in a battery of neuropsychological and cognitive function tests; serum BDNF concentration.

Results: Eight hundred twenty-seven participants (18.8%) had MCI. After adjustment for sex, age, education level, diabetes, and current smoking, serum BDNF was associated with poorer performance in the story memory, and digit symbol substitution task scores. Serum BDNF was marginally associated with the presence of MCI (odds ratio, 95% confidence interval: 1.41, 1.00–1.99) when BDNF was 1.5 SD lower than the mean value standardized for sex and age, education level, diabetes, and current smoking.

Conclusion: Low serum BDNF was associated with lower cognitive test scores and MCI. Future prospective studies should establish the discriminative value of serum BDNF for the risk of MCI.

The association between low vitamin D and depressive disorders

It has been hypothesized that hypovitaminosis D is associated with depression but epidemiological evidence is limited. We investigated the association between depressive disorders and related clinical characteristics with blood concentrations of 25-hydroxyvitamin D [25(OH)D] in a large cohort. The sample consisted of participants (aged 18-65 years) from the Netherlands Study of Depression and Anxiety (NESDA) with a current (N=1102) or remitted (N=790) depressive disorder (major depressive disorder, dysthymia) defined according to DSM-IV criteria, and healthy controls (N=494). Serum levels of 25(OH)D measured and analyzed in multivariate analyses adjusting for sociodemographics, sunlight, urbanization, lifestyle and health. Of the sample, 33.6% had deficient or insufficient serum 25(OH)D (<50 nmol l(-1)). As compared with controls, lower 25(OH)D levels were found in participants with current depression (P=0.001, Cohen's d=0.21), particularly in those with the most severe symptoms (P=0.001, Cohen's d=0.44). In currently depressed persons, 25(OH)D was inversely associated with symptom severity (β=-0.19, s.e.=0.07, P=0.003) suggesting a dose-response gradient, and with risk (relative risk=0.90, 95% confidence interval=0.82-0.99, P=0.03) of having a depressive disorders at 2-year follow-up. This large cohort study indicates that low levels of 25(OH)D were associated to the presence and severity of depressive disorder suggesting that hypovitaminosis D may represent an underlying biological vulnerability for depression. Future studies should elucidate whether-the highly prevalent-hypovitaminosis D could be cost-effectively treated as part of preventive or treatment interventions for depression.

The Brain Derived Neurotrophic Factor and Personality

The study of the biological basis of personality is a timely research endeavor, with the aim of deepening our understanding of human nature. In recent years, a growing body of research has investigated the role of the brain derived neurotrophic factor (BDNF) in the context of individual differences across human beings, with a focus on personality traits. A large number of different approaches have been chosen to illuminate the role of BDNF for personality, ranging from the measurement of BDNF in the serum/plasma to molecular genetics to (genetic) brain imaging. The present review provides the reader with an overview of the current state of affairs in the context of BDNF and personality.

Association between serum brain-derived neurotrophic factor and plasma interleukin-6 in major depressive disorder with melancholic features

Inflammatory processes as well as attenuation of brain-derived neurotrophic factor (BDNF) availability are involved in the pathophysiology of major depressive disorder (MDD). Although it is generally presumed that these two systems interact negatively in the brain, preclinical and human in vitro studies have shown synergistic rather than antagonistic interactions in the periphery. We therefore examined the association between serum levels of BDNF and plasma levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in patients with MDD (n=1070) and non-depressed controls (n=379) from the Netherlands Study of Depression and Anxiety. We used multiple regression analyses with serum BDNF as the dependent variable and we specifically tested the presence of BDNF-cytokine associations in DSM-IV-assigned melancholic MDD patients, identified by the Inventory of Depressive Symptomatology. After adjustment for sociodemographics, sampling variability, lifestyle indicators, somatic diseases and medication use, BDNF levels were predicted by the interaction between MDD diagnosis and IL-6 (p-interaction=.006). Stratified analyses showed that BDNF levels are indeed positively associated with IL-6 levels in MDD patients (β=.07, p=.02), but not in non-depressed controls (β=-.07, p=.23). When further stratified for melancholic and non-melancholic MDD (p-interaction=.005), IL-6 emerged as a robust positive predictor of BDNF only in the melancholic sample (β=.21, p=.01), wherein serum BDNF levels were accordingly enhanced. Post-hoc exploratory analyses verified an accentuated positive association of BDNF levels with leucocyte counts in melancholia. No significant associations emerged between BDNF and TNF-α. Overall, our cross-sectional approach may have disclosed an allostatic, BDNF-inducing component of peripheral immunity and/or an immunotrophic function of peripheral BDNF. Both scenarios may warrant further exploration, as they could inform new research concepts towards immune-based antidepressive treatment strategies.