Major depressive disorder (MDD) is a debilitating disease that is characterized by depressed mood, diminished interests, impaired cognitive function and vegetative symptoms, such as disturbed sleep or appetite. MDD occurs about twice as often in women than it does in men and affects one in six adults in their lifetime. The aetiology of MDD is multifactorial and its heritability is estimated to be approximately 35%. In addition, environmental factors, such as sexual, physical or emotional abuse during childhood, are strongly associated with the risk of developing MDD. No established mechanism can explain all aspects of the disease. However, MDD is associated with alterations in regional brain volumes, particularly the hippocampus, and with functional changes in brain circuits, such as the cognitive control network and the affective-salience network. Furthermore, disturbances in the main neurobiological stress-responsive systems, including the hypothalamic-pituitary-adrenal axis and the immune system, occur in MDD. Management primarily comprises psychotherapy and pharmacological treatment. For treatment-resistant patients who have not responded to several augmentation or combination treatment attempts, electroconvulsive therapy is the treatment with the best empirical evidence. In this Primer, we provide an overview of the current evidence of MDD, including its epidemiology, aetiology, pathophysiology, diagnosis and treatment.

Aims/hypothesis There is evidence that type 2 diabetes mellitus is associated with cognitive impairment. Most studies investigating this association have evaluated elderly individuals, after many years of diabetes, who generally have poor glycaemic control and significant vascular disease. The aim of the current study was to investigate the early cognitive consequences and associated brain correlates of type 2 diabetes. Materials and methods With regard to cognition and brain measures, we compared 23 age-, sex-and educationmatched control subjects with 23 mostly middle-aged individuals with relatively well-controlled diabetes of less than 10 years from the time of diagnosis. Results We found deficits in hippocampal-based memory performance and preservation of other cognitive domains. Relative to control subjects, individuals with diabetes had reductions in brain volumes that were restricted to the hippocampus. There was an inverse relationship between glycaemic control and hippocampal volume; in multivariate regression analysis, HbA 1c was the only significant predictor of hippocampal volume, accounting for 33% of the observed variance. Other variables commonly associated with type 2 diabetes, such as elevated BMI, hypertension or dyslipidaemia, did not independently contribute to the variance in hippocampal volume. Conclusions/interpretation These results suggest that the medial temporal lobe may be the first brain site affected by type 2 diabetes and that individuals in poorer metabolic control may be affected to a greater extent.

Multiple sclerosis is a heterogeneous disease with varying clinical picture. There have been substantial efforts to develop outcome measurements for therapeutic interventions but very few studies have addressed the value of bodily functions from the patient perspective. In a randomly selected cohort of early (<5 years, n=84) and longer lasting disease courses (>15 years, n=82) patients we asked for a weighting of 13 bodily functions and compared results with actual disability as measured by the United Kingdom Disability Scale. Lower limb function was given the highest priority in both patient groups followed by visual functioning and cognition especially in longer lasting MS. Actual disability did not correlate with the given priorities indicating that experienced deficits do not influence the subjective ratings of bodily functions. These results underline that ambulation-focused scales in MS represent a key dimension from the patient perspective. Visual functioning should be taken more into account.

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Background: Exercise may have beneficial effects on both well-being and walking ability in multiple sclerosis (MS). Exercise is shown to be neuroprotective in rodents and may also enhance cognitive function in humans. It may, therefore, be particularly useful for MS patients with pronounced neurodegeneration. Objective: To investigate the potential of standardized exercise as a therapeutic intervention for progressive MS, in a randomized-controlled pilot trial. Methods: Patients with progressive MS and moderate disability (Expanded Disability Status Scale (EDSS) of 4-6) were randomized to one of three exercise interventions (arm ergometry, rowing, bicycle ergometry) for 8-10 weeks or a waitlist control group. We analyzed the drop-out rate as a measure of feasibility. The primary endpoint of the study was aerobic fitness. Secondary endpoints were walking ability, cognitive function as measured by a neuropsychological test battery, depression and fatigue. Results: A total of 42 patients completed the trial (10.6% drop-out rate). Significant improvements were seen in aerobic fitness. In addition, exercise improved walking ability, depressive symptoms, fatigue and several domains of cognitive function. Conclusion: This study indicated that aerobic training is feasible and could be beneficial for patients with progressive MS. Larger exercise studies are needed to confirm the effect on cognition. Trial Registration: ISRCTN (trial number 76467492) http://isrctn.org

The pathogenesis of multiple sclerosis (MS) involves complex interactions between genetic susceptibility and environmental triggers. Clinical observations suggest that the study of sex differences may provide important insight into mechanisms of MS pathogenesis and progression. One clinical observation is that MS occurs more frequently in women than in men, indicating an impact of sex-related factors on susceptibility to MS. These factors include hormonal, genetic, and environmental influences, as well as gene x environment interactions and epigenetic mechanisms. Despite a higher incidence and more robust immune responses, females do not have a poorer prognosis, suggesting a biological mechanism of resilience. A second clinical observation is the pregnancy strongly affects disease activity, leading to a reduction in relapse rates in the last trimester but an increase post partum. However, pregnancy has little effects on long-term disability. Unraveling mechanisms underlying these clinical observations at the laboratory bench, with subsequent translation back to the bedside is a unique and potentially fruitful strategy in MS. In this paper, we review the current knowledge in the field and discuss novel therapeutic approaches currently in development that were derived from the study of sex-related factors.

These data support a role for the C1q-C3 complement axis in synaptic alterations in the MS hippocampus.

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