Cognitive Dysfunction in Major Depressive Disorder: Effects on Psychosocial Functioning and Implications for Treatment

Abstract

Major depressive disorder is a common condition with a high rate of recurrence, chronicity, and staggering economic burden, including disability in the workforce.1 In 2010, MDD was the second leading medical cause of burden globally, with highest estimates of disability in people of working age.2 In Canada, the annual prevalence of MDD is 3% to 4% overall, and 79% of people with MDD report some interference with work functioning, either decreased work productivity and (or) absenteeism.1 In addition to work impairment, the psychosocial impact of MDD often affects a person's level of functioning in family and social relationships. While there is clearly an association between improvement in depressive symptoms and functioning, symptom improvement can also be dissociated from functional improvement and work loss.3,4 Hence there has been increasing recognition that symptomatic remission is an insufficient goal of treatment for MDD and that return to premorbid psychosocial functioning should be targeted. 5Cognitive dysfunction refers to deficits in attention, verbal and nonverbal learning, short-term and working memory, visual and auditory processing, problem solving, processing speed, and motor functioning. Cognitive dysfunction may be a primary mediator of functional impairment in MDD. 6 Cognitive complaints are core symptoms of acute MDEs, and diminished ability to think or concentrate and (or) indecisiveness are criterion items for the diagnosis of MDD. Several other core symptoms of MDD may act as mediators of cognitive dysfunction, including psychomotor retardation, amotivation, fatigue, insomnia, and mood disturbances. Deficits on neuropsychological testing are well demonstrated in people with MDD, compared with healthy subjects, with many studies and meta-analyses showing moderate effect sizes in neurocognitive domains of processing speed, attention, executive function, learning, and memory 7,8 as well as in cognitive affective bias. Cognitive affective bias reflects distorted information processing and (or) focus moving away from positive stimuli and toward negative stimuli, 7 and abnormal responses to negative feedback and decision making. It is also apparent that, while cognitive dysfunction in MDD may improve with treatment and resolution of depressive symptoms, cognitive deficits can still be detected even in periods of symptom remission. In a 3-year, follow-up study of patients with MDD, the proportion of time with cognitive complaints was reported as 94% during acute depressive episodes; this remained at 44% despite full or partial symptom remission during treatment. 10 Cognitive performance on tests of immediate memory, attention, 11 and processing speed 12 was reported to be inferior in patients with MDD who met criteria for remission, compared with healthy subjects. Meta-analyses show that cognitive deficits in executive function are still present in remitted patients, 13,14 which may explain persistent psychosocial impairment in remission.While it is beyond the scope of our paper to review the unde...

The ‘cognitive footprint’ of psychiatric and neurological conditions: cross‐sectional study in the UK Biobank cohort

“…This impacts negatively on functional independence, educational and occupational attainment, and quality of life 4, 5, 6, 7, and cognitive improvement is therefore an increasing focus of treatment development efforts 8, 9, 10. Estimates of cognitive impairment prevalence in euthymic adults with mood disorder vary considerably, ranging from 5% to 58% in adults with bipolar disorder (BD) 11, and from one‐third to one‐half in those with major depressive disorder 12.…”

Domain-specific cognitive impairment in patients with COPD and control subjects

“…Indeed, deficits in cognitive performances are found in major depressive disorders. 38 Moreover, the higher prevalence of antidepressant use may partly account for the higher prevalence of cognitive impairment in patients compared to controls due to its sedative and anticholinergic effects. The dose, time since last administration, and plasma concentration of the drug, however, determine the extent to which cognitive performance is affected.…”

Latest Developments in Cognitive Functioning in Mood and Anxiety Disorders

“…Less research has been dedicated to determining the extent of cognitive deficits in MDD than has in severe mental illness such as schizophrenia and bipolar disorder [3], possibly because of the belief that these deficits are entirely caused by mood states. The impact of cognitive dysfunction on psychosocial function has also been relatively underevaluated [3,4]. Based on evidence that cognitive deficits may persist when other symptoms and core features of MDD resolve may indicate the need for a reconceptualization of symptomatic remission in MDD [3], much as functional remission has become a topic of discussion in other conditions such as schizophrenia [5].…”

“…Lam et al [4] hypothesized that the sometimes seemingly resistant functional outcomes (psychosocial and vocational outcomes) in MDD may be mediated by neurocognitive deficits, which also do not universally and reliably improve alongside symptoms. Lam et al [4] reviewed the literature examining deficits in neuropsychological functioning including attention, learning, working memory, visual and auditory processing, processing speed, motor functioning, and problem solving in the context of MDD.…”