Although monoaminergic-targeted drugs have prompted great advances in the development of treatments for depression, the need for new options persists, since these drugs still have a delayed clinical effect and most patients do not respond properly to them. Recently, the observation of the antidepressant effects of ketamine brought on a new wave of studies regarding the comprehension of the neurobiology of depression and the development of new and more effective antidepressant drugs.

Thus, in this paper, we present a historical review of the development of monoaminergic antidepressant drugs and the role of ketamine as the introductory agent of a new era in the research of the neurobiology of depression.

Firstly, we review how the pharmacological treatment for major depression started, and we point out the main drugs discovered, the researchers involved, and how the studies developed have contributed to the understanding of the neurobiology of depression. Secondly, the major problems regarding the clinical efficacy and acceptance of these drugs are discussed, and the introduction of the glutamatergic system as a target for antidepressant drugs is presented. Finally, we review how ketamine revealed itself as an exciting option towards obtaining pharmacological agents to treat depression, through the understanding of biological markers.

Ketamine contributed to confirm that different targets of the glutamatergic system and neurotrophic pathways are strictly related to the neurobiology of depression. There are several antidepressant drugs based on ketamine’s mechanism of action already in the pipeline, and glutamatergic-targeted antidepressants may be on the market in the near future.

A restricted Brief Psychiatric Rating Scale (BPRS-6) with the six schizophrenia specific items from the Positive and Negative Syndrome Scale (PANSS) has been investigated. These six items from the PANSS have recently been found to have both clinical validity and ‘unidimensionality’ in measuring the severity of schizophrenic states. The primary objective of this study was to evaluate the clinical validity of the BPRS-6. The secondary objective was to evaluate the ‘unidimensionality’ of the BPRS-6 by an ‘item response theory’ model.

The BPRS-6 was scored independently by two psychiatrists and two psychologists while viewing six open-ended videotaped interviews in patients with a DSM-III diagnosis of schizophrenia. The interviews were conducted by Heinz E. Lehmann, an experienced psychiatrist. They were focused on the psychopathology that contributed most to the ‘severity’ of the patient’s clinical state.

The BPRS-6 with three positive symptoms (delusions, conceptual disorganisation, hallucinations) and three negative symptoms (blunted affect, emotional withdrawal, poverty of speech) was found to be clinically valid and captured the variables that contribute most to the severity of schizophrenia. The BPRS-6 was also found to have acceptable ‘unidimensionality’ (coefficient of homogeneity 0.45) and inter-rater reliability (inter-class-coefficient 0.81).

The BPRS-6 was found to capture the information that translates into the severity of schizophrenia. It has also acceptable psychometric validity.

The objective of this review is to investigate existing literature in order to delineate whether the use of anaesthesia and timing of seizure induction in a new and optimised way may improve the efficacy of electroconvulsive therapy (ECT).

PubMed/MEDLINE was searched for existing literature, last search on 24 June 2015. Relevant clinical studies on human subjects involving choice of anaesthetic, ventilation and bispectral index (BIS) monitoring in the ECT setting were considered. The references of relevant studies were likewise considered.

Propofol yields the shortest seizures, etomidate and ketamine the longest. Etomidate and ketamine+propofol 1 : 1 seems to yield the seizures with best quality. Seizure quality is improved when induction of ECT is delayed until the effect of the anaesthetic has waned – possibly monitored with BIS values. Manual hyperventilation with 100% O2 may increase the pO2/pCO2-ratio, which may be correlated with better seizure quality.

Etomidate or a 1 : 1 ketamine and propofol combination may be the best method to achieve general anaesthesia in the ECT setting. There is a need for large randomised prospective studies comparing the effect of methohexital, thiopental, propofol, ketamine, propofol+ketamine 1 : 1 and etomidate in the ECT treatment of major depressed patients. These studies should investigate safety and side effects, and most importantly have antidepressant efficacy and cognitive side effects as outcome measures instead of seizure quality.

Electroconvulsive therapy (ECT) is a non-pharmacological treatment that is effective in treating severe and treatment-resistant depression. Although the efficacy of ECT has been demonstrated to treat major depressive disorder (MDD), the brain mechanisms underlying this process remain unclear. Structural–functional changes occur with the use of ECT as a treatment for depression based on magnetic resonance imaging (MRI). For this reason, we have tried to identify the changes that were identified by MRI to try to clarify some operating mechanisms of ECT. We focus to brain changes on MRI [structural MRI (sMRI), functional MRI (fMRI) and diffusion tensor imging (DTI)] after ECT.

A systematic search of the international literature was performed using the bibliographic search engines PubMed and Embase. The research focused on papers published up to 30 September 2015. The following Medical Subject Headings (MESH) terms were used: electroconvulsive therapy AND (MRI OR fMRI OR DTI). Papers published in English were included. Four authors searched the database using a predefined strategy to identify potentially eligible studies.

There were structural changes according to the sMRI performed before and after ECT treatment. These changes do not seem to be entirely due to oedema. This investigation assessed the functional network connectivity associated with the ECT response in MDD. ECT response reverses the relationship from negative to positive between the two pairs of networks.

We found structural–functional changes in MRI post-ECT. Because of the currently limited MRI data on ECT in the literature, it is necessary to conduct further investigations using other MRI technology.

Nitric oxide synthase (NOS) inhibitors induce antidepressant-like effects in animal models sensitive to acute drug treatment such as the forced swimming test. However, it is not yet clear if repeated treatment with these drugs is required to induce antidepressant-like effects in preclinical models.

The aim of this study was to test the effect induced by acute or repeated (7 days) treatment with 7-nitroindazole (7-NI), a preferential inhibitor of neuronal NOS, in rats submitted to the learned helplessness (LH) model. In addition, we aimed at investigating if 7-NI treatment would increase brain-derived neurotrophic factor (BDNF) protein levels in the hippocampus, similarly to the effect of prototype antidepressants.

Animals were submitted to a pre-test (PT) session with inescapable footshocks or habituation (no shocks) to the experimental shuttle box. Six days later they were exposed to a test with escapable footshocks. Independent groups received acute (a single injection after PT or before test) or repeated (once a day for 7 days) treatment with vehicle or 7-NI (30 mg/kg).

Repeated, but not acute, treatment with 7-NI attenuated LH development. The effect was similar to repeated imipramine treatment. Moreover, in an independent experimental group, only repeated treatment with 7-NI and imipramine increased BDNF protein levels in the hippocampus.

The results suggest the nitrergic system could be a target for the treatment of depressive-like conditions. They also indicate that, similar to the positive control imipramine, the antidepressant-like effects of NOS inhibition could involve an increase in hippocampal BDNF levels.

Bipolar disorder (BD) patients have recently been shown to exhibit increased proinflammatory cytokine levels indicating the role of inflammation in this disease. As inflammatory responses often include complement level alterations and complement production is influenced by cytokines, we aimed to find out whether complement system is activated in BD in a time-dependent manner and complement factors are involved in BD pathogenesis.

Serum C4, factor B, sC5b-9 and neuron-specific enolase levels were measured by enzyme-linked immunosorbent assay, whereas peripheral blood mononuclear cell messenger RNA (mRNA) expression levels of C1q, C4, factor B and CD55 were measured by real-time polymerase chain reaction in chronic BD patients (n=22), first episode BD patients (n=24) and healthy controls (n=19).

Serum complement levels were significantly reduced in chronic BD patients as compared with first episode BD patients and healthy controls. Serum levels of complement factors showed significant inverse correlation with disease duration, severity of manic symptoms and serum neuron-specific enolase levels. In chronic BD patients, peripheral blood mononuclear cell mRNA expression levels of C1q, C4 and factor B were significantly elevated, whereas the mRNA expression level of the complement inhibitor CD55 was significantly reduced.

Our results suggest that complement factor levels are reduced in BD presumably due to overconsumption of the complement system and complement production is increased at mRNA level possibly as a compensation measure. Complement factors might potentially be used as indicators of disease severity, neuronal loss and cognitive dysfunction.

Lack of good animal models for affective disorders, including major depression and bipolar disorder, is noted as a major bottleneck in attempts to study these disorders and develop better treatments. We suggest that an important approach that can help in the development and use of better models is attention to variability between model animals.

Differences between mice strains were studied for some decades now, and sex differences get more attention than in the past. It is suggested that one factor that is mostly neglected, individual variability within groups, should get much more attention. The importance of individual differences in behavioral biology and ecology was repeatedly mentioned but its application to models of affective illness or to the study of drug response was not heavily studied. The standard approach is to overcome variability by standardization and by increasing the number of animals per group.

Possibly, the individuality of specific animals and their unique responses to a variety of stimuli and drugs, can be helpful in deciphering the underlying biology of affective behaviors as well as offer better prediction of drug responses in patients.

Electroconvulsive therapy (ECT) is regularly used to treat patients with severe major depression, but the mechanisms underlying the beneficial effects remain uncertain. Electroconvulsive stimulation (ECS) regulates diverse neurotransmitter systems and induces anticonvulsant effects, properties implicated in mediating therapeutic effects of ECT. Somatostatin (SST) is a candidate for mediating these effects because it is upregulated by ECS and exerts seizure-suppressant effects. However, little is known about how ECS might affect the SST receptor system. The present study examined effects of single and repeated ECS on the synthesis of SST receptors (SSTR1–4) and SST, and SST receptor binding ([125I]LTT-SST28) in mouse hippocampal regions and piriform/parietal cortices.

A complex pattern of plastic changes was observed. In the dentate gyrus, SST and SSTR1 expression and the number of hilar SST immunoreactive cells were significantly increased at 1 week after repeated ECS while SSTR2 expression was downregulated by single ECS, and SSTR3 mRNA and SST binding were elevated 24 h after repeated ECS. In hippocampal CA1 and parietal/piriform cortices, we found elevated SST mRNA levels 1 week after repeated ECS and elevated SST binding after single ECS and 24 h after repeated ECS. In hippocampal CA3, repeated ECS increased SST expression 1 week after and SST binding 24 h after. In the parietal cortex, SSTR2 mRNA expression was downregulated after single ECS while SSTR4 mRNA expression was upregulated 24 h after repeated ECS.

Considering the known anticonvulsant effects of SST, it is likely that these ECS-induced neuroplastic changes in the SST system could participate in modulating neuronal excitability and potentially contribute to therapeutic effects of ECT.

This study aimed to explore effects of adjunctive treatment with N-acetyl cysteine (NAC) on markers of inflammation and neurogenesis in bipolar depression.

This is a secondary analysis of a placebo-controlled randomised trial. Serum samples were collected at baseline, week 8, and week 32 of the open-label and maintenance phases of the clinical trial to determine changes in interleukin (IL)-6, IL-8, IL-10, tumour necrosis factor-α (TNF-α), C-reactive protein (CRP) and brain-derived neurotrophic factor (BDNF) following adjunctive NAC treatment, and to explore mediation and moderator effects of the listed markers.

Levels of brain-derived neurotrophic factor (BDNF), tumour necrosis factor-α (TNF-α), C-reactive protein (CRP), interleukins (IL) -6, 8, or 10 were not significantly changed during the course of the trial or specifically in the open-label and maintenance phases. There were no mediation or moderation effects of the biological factors on the clinical parameters.

The results suggest that these particular biological parameters may not be directly involved in the therapeutic mechanism of action of adjunctive NAC in bipolar depression.

To evaluate the performances of two auditory brainstem response (ABR) profiling tests as potential biomarkers and diagnostic support for schizophrenia and adult attention-deficit hyperactivity disorder (ADHD), respectively, in an investigator-initiated blinded study design.

Male and female patients with schizophrenia (n=26) and adult ADHD (n=24) meeting Diagnostic and Statistical Manual of Mental Disorders Fourth Edition (DSM IV) diagnostic criteria and healthy controls (n=58) comprised the analysis set (n=108) of the total number of study participants (n=119). Coded sets of randomized ABR recordings were analysed by an independent party blinded to clinical diagnoses before a joint code-breaking session.

The ABR profiling test for schizophrenia identified schizophrenia patients versus controls with a sensitivity of 84.6% and a specificity of 93.1%. The ADHD test identified patients with adult ADHD versus controls with a sensitivity of 87.5% and a specificity of 91.4%.

The ABR profiling tests discriminated schizophrenia and ADHD versus healthy controls with high sensitivity and specificity. The methods deserve to be further explored in larger clinical studies including a broad range of psychiatric disorders to determine their utility as potential diagnostic biomarkers.

This study investigated immersive virtual reality (IVR), as a novel technique to test executive function of healthy younger and older adults. We predicted IVR tasks to have greater predictive power than traditional measures when assessing age-related cognitive functioning due to the real-world validity of the tasks.

Participants (n=40) completed the Stroop colour–word test and the trail-making test (TMT) as traditional and commonly used assessments of executive functioning. Participants then completed three IVR tasks; a seating arrangement task, an item location task (both set in a virtual chemistry lab), and a virtual parking simulator.

Younger adults completed significantly more parking simulator levels (p<0.001), placed significantly more objects (p<0.001), and located significantly more items than older adults (p<0.01), demonstrating higher levels of performance. Significant correlations were found between performance on traditional neuropsychological measures and IVR measures. For example, Stroop CW performance significantly correlated with the number of parking simulator levels completed (τ=0.43, p<0.01). This suggests that IVR measures assess the same underlying cognitive constructs as traditional tasks. In addition, IVR measures contributed a significant percentage of the explained variance in age.

IVR measures (i.e. number of parking simulator levels completed and number of objects placed in the seating arrangement task) were found to be stronger contributors than existing traditional neuropsychological tasks in predicting age-related cognitive decline. Future research should investigate the implementation of these real-world-based tasks in clinical groups given this promising initial work.

According to a recent study, ratings on the Psychotic Depression Assessment Scale (PDAS) obtained via a dedicated semi-structured interview are valid measures of the severity of psychotic depression. This study aimed to further test the validity, scalability and responsiveness of the PDAS in older adults using independent ratings on the Clinical Global Impression Scale – Severity (CGI-S) and the Montgomery-Asberg Depression Rating Scale (MADRS) as references.

Ratings were performed at admission and discharge at two old age psychiatric wards in Flanders, Belgium. In total, 62 older adults (mean age: 74.3 years) with psychotic depression were included. The PDAS was rated by trained nurses using the semi-structured PDAS interview. Senior psychiatrists scored the participants on the CGI-S. Psychologists or experienced nurses rated participants on the MADRS. Clinical validity was assessed by correlating the PDAS total scores with CGI-S ratings and MADRS total scores. Mokken analysis was performed to assess the scalability of the PDAS. Responsiveness was assessed by comparing the proportion of participants in remission (PDAS total score <8 at study baseline and endpoint).

The Spearman correlation coefficients were 0.76 and 0.79 for the PDAS versus CGI-S and PDAS versus MADRS, respectively. The Mokken analysis yielded a Loevinger coefficient of 0.46, which is indicative of scalability. At admission, no participants met the PDAS remission criterion. At discharge, 54% (95% confidence interval: 47%–60%) of the patients met this criterion.

The PDAS appears to be a clinically valid, scalable and responsive measure of the severity of psychotic depression in older adults.

Prior studies have indicated that both high and low school grades are associated with development of bipolar disorder (BD), but these studies have not adjusted for parental history of mental disorder, which is a likely confounder. Furthermore, the association between school grades and bipolar I disorder (BD-I) has not been studied. Therefore, we aimed to study the association between school exam grades and subsequent development of BD and BD-I while adjusting for parental history of mental disorder.

We conducted a register-based nationwide cohort study following 505 688 individuals born in Denmark between 1987 and 1995. We investigated the association between school exam grades and development of BD or BD-I with a Cox model adjusting for family history of mental disorder and other potential confounders.

During follow-up, 900 individuals were diagnosed with BD and 277 of these with BD-I. The risk for BD and BD-I was significantly increased for individuals not having completed the exams at term [adjusted hazard ratio (aHR) for BD (aHR=1.71, 95% CI: 1.43–2.04) and for BD-I (aHR=1.57, 95% CI: 1.13–2.19)]. Also, having low exam grades in mathematics was associated with increased risk of both BD (aHR=2.41, 95% CI: 1.27–4.59) and BD-I (aHR=2.71, 95% CI: 1.41–5.21). Females with very high exam grades in Danish (percentile group>97.7) had a significantly increased risk of BD-I (aHR=2.49, 95% CI: 1.19–5.23).

The potential to develop BD seems to affect the school results of individuals negatively even before BD is diagnosed – with females having the potential to develop BD-I as a possible exception.