About this Research Topic
Mood disorders are common, complex and costly neuropsychiatric disorders which occur at all ages and in all demographic groups. Modern diagnostic schemes differentiate between Major Depressive Disorder and Bipolar Disorders, but there is much overlap between these categories. Traditionally defined by symptom clusters (i.e., mania, depression or mixtures thereof), it is now increasingly recognised that other aspects of these disorders may play an important role in the fundamental disease processes and the mechanism of action of treatments. The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) includes cognitive symptoms as one of the nine diagnostic criteria for major depressive episode which can occur in the context of major depression or bipolar disorder. Cognitive impairment in patients with mood disorders is being recognised as a significant factor that can have an impact on patients’ ability to function and on their recovery from their mood disorder and as a result is viewed as a target for therapeutic intervention.
Cognitive problems in depression are a core symptom and clinically important, resulting in problems such as poor concentration, memory and decision making, with patients describing their ‘mind going blank’ and complaining of an inability to make decisions. Indeed, patients may think they have attention-deficit disorder or, if older, Alzheimer’s disease. Such cognitive symptoms may persist after an episode of mood disorder so there may be residual symptoms, which has implications for the management of patients with mood disorders and for the ability to achieve functional recovery even after the episode ends.
Cognitive impairment manifests across many mental illnesses and can affect attention, learning and memory, and the speed of mental processing. Indeed, neuropsychological testing can be used in a simple and practicable fashion to interface with many of the other imaging techniques and measures of brain function to measure and demonstrate cognitive changes. But the important aspect is how treatment impacts on real-world functioning. A therapy that shows changes in sophisticated measuring techniques is of no great value unless those changes translate into practical benefits that impact on patients’ day-to-day lives. Indeed, there is evidence that cognitive dysfunction is not just a proxy measure that can be used in testing for drug discovery – it has an impact on real-world functioning and is therefore a major contributor to the economic burden of depression and bipolar disorders.
The papers in this Research Topic will review a number of aspects of cognition in mood disorders which are important areas of clinical and research focus. These will include the natural history and neurobiological underpinnings of cognitive impairment in mood disorders; measurement of cognition in mood disorders; the relationship between treatment and cognition and the evidence of emerging benefits of various treatment modalities on cognitive impairment in mood disorders.
Keywords: Cognition, Neuropsychology, Depression, Bipolar, Neuroscience