ReviewComputerized cognitive training and functional recovery in major depressive disorder: A meta-analysis
Introduction
Major depressive disorder (MDD) is a common disorder among adults with a lifetime prevalence of 16.6% in the United States (Kessler et al., 2005). Depression is associated with greater psychosocial disability (Judd et al., 2000), higher functional impairment (Rapaport et al., 2005), and higher rates of mortality (Cuijpers and Smit, 2002). Depressed adults are at greater risk of developing anxiety disorders (Kessler et al., 2008) and cardiovascular diseases, such as ischemic heart disease and cerebrovascular disease (Holt et al., 2013). In terms of everyday functioning, lack of energy, loss of interest, apathy, and insomnia make it difficult to complete daily tasks. An estimated 7% of depressed adults commit suicide, largely in part due to lack of treatment or low treatment efficacy (Bostwick and Pankratz, 2000). It is estimated that only 37.5% of adults receive minimally adequate treatment (Wang et al., 2005). Beyond the impairment to health, depression is responsible for low productivity, missed work days, and an estimated $83 billion dollars in economic loss annually (Greenberg et al., 2003).
In addition to physical health problems, depression often manifests with cognitive impairment. Specifically, depressed individuals have deficits in working memory, verbal fluency, processing speed, attention, and executive function (Austin et al., 2001). Impairment in cognitive functions in depressed adults predicts low functional outcome as well as treatment nonresponse (Alexopoulos et al., 2005, Dunkin et al., 2000, Gorlyn et al., 2008, Kampf-Sherf et al., 2004). Further, these deficits are linked with reduced quality of life (Jaeger et al., 2006). While treatments such as psychotherapy and antidepressants have proven efficacy for improving mood, cognitive deficits often remain following remission (Baune et al., 2010, Paelecke-Habermann et al., 2005). It is essential that treatments address cognitive impairments, as they are a risk factor for suicide attempts and development of dementia (Keilp et al., 2001). Development of novel interventions to improve antidepressant response can have an enormous public health benefit.
One approach beginning to receive attention is computerized cognitive training (CCT) (Morimoto et al., 2012, Porter et al., 2013), in which cognitive exercises or games are used to target specific neural networks in order to improve cognitive functioning through neuroplasticity. CCT has been used in healthy adult populations (Mahncke et al., 2006, Stern et al., 2011, Willis et al., 2006) as well as in a variety of diagnostic conditions including attention-deficit hyperactivity disorder (Rapport et al., 2013), schizophrenia (Wykes et al., 2011), bipolar disorder (Preiss et al., 2013), traumatic brain injury (Salazar et al., 2000), mild cognitive impairment (Li et al., 2011), and Alzheimer's disease (Sitzer et al., 2006). It is administered through an automated computer program, oftentimes accessible over the internet. Advantages CCT hold over existing treatments for depression are that it is relatively inexpensive, noninvasive, and can be tailored to meet the specific cognitive needs of the individual. Further, there is no concern for medicinal side effects and training can be completed in the patient's own home. Because CCT necessitates computer access and sometimes an internet connection, it may be difficult to implement for populations that traditionally have low computer access, such as those with low household income and older adults.
The growth of CCT as an intervention is met with contention in regards to its effectiveness. Proponents highlight systematic reviews claiming CCT improves cognitive abilities in various patient populations, with some evidence of these benefits transferring to everyday functioning (Mahncke, 2014). Skeptics criticize the manufacturer's claims that CCT leads to increased mental fitness as being overstated and potentially misleading to patients and consumers (Max Planck Institute for Human Development and Stanford Center on Longevity, 2014). There is little evidence that the cognitive benefits are broad, and performance gains may reflect similarity between training paradigms and neuropsychological measures. Even when positive results are found, studies often lack methodological rigor to account for participant motivation and expectancy. The current debate demonstrates the urgent need for answers to questions about the value of CCT.
The purpose of this meta-analysis is to evaluate the efficacy of CCT for depressed individuals. In doing so, we attempt to answer several important questions. First, does CCT improve cognition, and in what domains? Depression is associated with numerous cognitive impairments, making it critical to understand which, if any, can be improved by CCT. Secondly, does it improve mood? Alleviation of cognitive impairments may enhance ongoing treatments, as might completion of rewarding tasks distract from ruminative thoughts. Finally, does the improvement transfer to everyday life functioning? While enhancing cognitive abilities is the immediate objective of CCT, it is done with the expectation that this facilitates improved quality of life. The absence of transfer would make it difficult to conclude CCT is not merely teaching to the test.
Section snippets
Method
PRISMA guidelines for conducting and reporting systematic reviews were followed during this analysis (Moher et al., 2009).Studies for the meta-analysis were selected using PsycINFO and MEDLINE. The following keywords were used: “Cognitive training” or “Cognitive remediation” or “Cognitive rehabilitation” and “Depression.” Results were further limited to (1) English language articles, (2) participants aged 18 years or greater, and (3) study design of clinical trial, controlled clinical trial,
Results
Nine studies met criteria for inclusion in our study (Alvarez et al., 2008, Bowie et al., 2013, Calkins et al., 2014, Elgamal et al., 2007, Lohman et al., 2013, Naismith et al., 2011, Owens et al., 2013, Segrave et al., 2014, Siegle et al., 2014). Across all studies, the average participant age was 44.1% and 55.0% were female. There were no significant differences between the CCT groups and control groups on the basis of demographics such as age, gender, or education. Table 1 summarizes
Discussion
The purpose of this meta-analysis was to assess the impact of CCT on depression; in particular, whether CCT improves depressed mood, daily functioning, and five domains of cognitive functioning (attention, executive functioning, verbal memory, working memory, global functioning). The results of our meta-analysis reveal small to large effects for CCT on depressed mood, daily functioning, and three of five cognitive domains assessed (attention, working memory, and global functioning), suggesting
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