Processing of facial expressions of emotion is central to human interaction, and has important effects on behaviour and affective state. A range of methods and paradigms have been used to investigate various aspects of abnormal processing of facial expressions in major depression, including emotion specific deficits in recognition accuracy, response biases and attentional biases. The aim of this review is to examine and interpret data from studies of facial emotion processing in major depression, in the context of current knowledge about the neural correlates of facial expression processing of primary emotions. The review also discusses the methodologies used to examine facial expression processing. Studies of facial emotion processing and facial emotion recognition were identified up to December 2009 utilizing MEDLINE and Web of Science. Although methodological variations complicate interpretation of findings, there is reasonably consistent evidence of a negative response bias towards sadness in individuals with major depression, so that positive (happy), neutral or ambiguous facial expressions tend to be evaluated as more sad or less happy compared with healthy control groups. There is also evidence of increased vigilance and selective attention towards sad expressions and away from happy expressions, but less evidence of reduced general or emotion-specific recognition accuracy. Data is complicated by the use of multiple paradigms and the heterogeneity of major depression. Future studies should address methodological problems, including variations in patient characteristics, testing paradigms and procedures, and statistical methods used to analyse findings.

Neuropsychological impairment is well established as a feature of major depressive disorder (MDD) but studies have shown a variable pattern of impairment. This paper seeks first to clarify this by examining methodological and clinical factors that give rise to variability in study findings. Second, it examines theories of the origin of these neuropsychological abnormalities. Third, it reviews evidence regarding the clinical significance of different patterns of deficit. A selective review was undertaken of the literature with a particular emphasis on methodological factors, the influence of clinical subtypes and prevalent theories of neuropsychological abnormality. Methodological issues and the heterogeneity of MDD account for considerable variability in results. Specific investigation of the subtypes of psychotic MDD, melancholic MDD and bipolar depression reduces this heterogeneity and results are more consistent in the elderly. Hypothalamic-pituitary-adrenal axis dysfunction is associated with neuropsychological dysfunction in MDD although evidence of direct causation is not definitive at present. Impairment of executive and psychomotor function is a consistent finding, particularly in the elderly, and may reflect frontostriatal-limbic dysfunction. There is growing evidence that this may have clinical significance. It is suggested that future research take very careful account of the exact phenotype of MDD. Classification based on neuropsychological profile may, in fact, be useful. Further research should examine further the clinical importance of patterns of neuropsychological impairment.

The study confirms a significant impairment in neuropsychological function in a clinical sample of outpatients with MDE, which is likely to have important implications for day-to-day functioning and treatment.

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Persisting impairment in neuropsychological functioning after the first 16 weeks of CBT or ST suggests a need to modify psychological treatments to include components targeting cognitive functioning.