Abstract
Background
Cognitive deficits are commonly observed in people diagnosed with schizophrenia and have been found to be more predictive of future daily and community functioning than the severity of clinical symptoms (e.g., hallucinations and delusions). Cognitive remediation (CR) is a psychological treatment developed to improve cognitive functioning and thereby daily functioning. Despite the effectivity of CR programs, reduced neuroplasticity in brain networks underlying the cognitive tasks may impede the effectiveness of these treatment programs. Increasing the neuroplasticity in these networks by the use of non-invasive brain stimulation (NIBS) like transcranial direct current stimulation or transcranial magnetic stimulation might boost the effect of CR. In a systematic review, we will address the question whether the combination of non-invasive brain stimulation and cognitive remediation may be a promising treatment strategy. We will apply a transdiagnostic perspective in order to determine the potential benefit of combining CR and NIBS in general, and not specific to a diagnostic category.
Methods
A systematic review of literature was conducted by searching PsycINFO, Pubmed, Web of Science, and Medline databases for combined treatments of CR and NIBS. Included studies were assessed for cognitive, clinical and functional outcomes.
Results
64 studies were identified, with 40 studies including clinical populations (e.g., schizophrenia, Alzheimer’s disease, HIV, MS). The cognitive outcomes showed mixed results. Most effects were found on complex attention and executive functioning. In these domains about 38% of the studies found an added positive treatment effect for combining interventions, in comparison to single interventions (i.e. CR, NIBS, or CR+sham-stimulation). Functional outcome measures were included in ten of the 40 studies with clinical populations. Eight studies found a positive trend towards greater improvements in daily functioning when CR and NIBS were combined.
Discussion
So far, findings indicate promising effects of combining CR and NIBS on cognitive functioning and daily functioning in healthy and various clinical populations. There is a lot of variety between studies (e.g., duration of treatment, number of total sessions, number of weekly sessions, cognitive domains targeted) which may explain the mixed results. Especially, the design of the CR varied widely. Strategy-use and targeting meta-cognition, which were identified as effective elements of CR as a stand-alone treatment were not included in many combined CR+NIBS designs. Future studies have to elucidate whether the combining CR (including strategy-use and meta-cognition) and NIBS has an additive effect on cognitive and/or daily functioning compared to non-combined treatment. Moreover, future studies should evaluate whether beneficial effects from the experimental studies translate into long-term improvement in activities of daily life.
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