Bernhard T. Baune - Cognitive Dimensions of Major Depressive Disorder

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Cognitive Dimensions of Major Depressive Disorder

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Major depressive disorder (MDD) is a clinically and neurobiologically highly heterogenous mood disorder that consists of a variety of symptom clusters including mood symptoms, physical symptoms, and cognitive symptoms. While the traditional model of depression implicates mood as the primary symptom cluster, a more recently published conceptual understanding of depression has been extended to also include cognitive symptoms. Moreover, the understanding of the central role of cognitive processes in emotion processing, social interaction, and pure cognitive performance has led to a model that places cognitive processing central to the pathophysiology of depression.

Cognitive dimensions of depression have long been implicated in the nature of depression that is characterized typically by impaired cognitive and emotional processes. In the following volume the dimensions of cognitive function, emotion processing, and social cognitive processing are highlighted to comprehensively describe large parts of the clinical symptoms, as well as the pathophysiology and biology, of the brain-based disorder of depression. The focus on the cognitive and emotional dimensions of depression offers extended and novel diagnostic and treatment approaches ranging from pharmacological to psychological interventions targeting those dimensions of depression.

This volume will attempt to inform about some of the more fundamental psychological, biological, and clinical concepts that are applicable to the comprehensive treatment of depression. The volume is suitable for students, trainees, clinicians, and scientists in the fields of psychology, neuropsychology, psychiatry, cognitive neuroscience, neurology, general medicine/general practice, and other health care professionals as it will also cover core knowledge and skills for training as well as practice.

Bernhard T. Baune

). Recent evidence suggests that cognitive dysfunction persists following symptomatic remission, highlighting the need to treat cognition separately from mood symptoms. Residual cognitive deficits may contribute to ongoing occupational and social dysfunction and promote suicide ideation. In addition, retention of cognitive impairment may interact with existing emotional and social vulnerability, increasing the risk of recurrent depressive episodes.

Figure 1.1 Domains of emotional, nonemotional, and social cognitive function

Current reviews suggest broad cognitive deficits in MDD, which are associated with impaired daily and psychosocial functioning. However, there is no firm consensus regarding which domains of cognition are selectively affected by depression, and hence which domains should be primary treatment targets. This uncertainty is caused in part by varied patterns of comorbidity and individual differences which affect cognitive functioning. However, ambiguous terminology and conceptual understanding of cognitive domains also contribute to uncertainty regarding cognitive deficitsan issue identified by authors who face difficulty in comparing cognitive functioning between studies.

Recent literature has identified impairment across several executive domains, including set shifting, inhibition, working memory, and verbal processing. Models of cognition and MDD underscore the vital importance of executive functioning in daily life and psychosocial abilities, suggesting that executive impairment may be a primary barrier to functional recovery in individuals with MDD. Although the domain-specific nature of executive impairment remains to be drawn out, current work supports the notion that executive remediation should be a primary target of cognitive treatment. Verbal processing, attention, learning, and memory also appear to be impaired by MDD. Given the importance of verbal memory and attention in occupational and social settings, it stands to reason that impairment in these domains may disrupt psychosocial functioning. Recent reports of impaired visuospatial processing in MDD are not consistent. However, patients with psychotic symptoms typically demonstrate lower visuospatial skills than depressed patients without psychoses, highlighting the need to consider comorbid illness and personalized treatment. The importance of visuospatial cognition in functional recovery may depend on the primacy of visuospatial skills in individuals occupational and everyday activities; however, this notion is yet to be empirically tested. Self-reported cognitive dysfunction is widely reported; however, there are inconsistent accounts as to whether subjective evaluations of cognition correlate with objective tests, or with real-world functioning.