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.

Background A fundamental challenge for many people with severe mental illness (SMI) is how to deal with cognitive impairments. Cognitive impairments are common in this population and limit daily functioning. Moreover, neural plasticity in people with SMI appears to be reduced, a factor that might hinder newly learned cognitive skills to sustain. The objective of this pilot trial is to investigate the effects of cognitive remediation (CR) on cognitive and daily functioning in people dependent on residential settings. In addition, transcranial direct current stimulation (tDCS) is used to promote neural plasticity. It is expected that the addition of tDCS can enhance learning and will result in longer-lasting improvements in cognitive and daily functioning. Methods This is a pragmatic, triple-blinded, randomized, sham-controlled, pilot trial following a non-concurrent multiple baseline design with the participants serving as their own control. We will compare (1) CR to treatment as usual, (2) active/sham tDCS+CR to treatment as usual, and (3) active tDCS+CR to sham tDCS+CR. Clinical relevance, feasibility, and acceptability of the use of CR and tDCS will be evaluated. We will recruit 26 service users aged 18 years or older, with a SMI and dependent on residential facilities. After a 16-week waiting period (treatment as usual), which will serve as a within-subject control condition, participants will be randomized to 16 weeks of twice weekly CR combined with active (N = 13) or sham tDCS (N = 13). Cognitive, functional, and clinical outcome assessments will be performed at baseline, after the control (waiting) period, directly after treatment, and 6-months post-treatment. Discussion The addition of cognitive interventions to treatment as usual may lead to long-lasting improvements in the cognitive and daily functioning of service users dependent on residential facilities. This pilot trial will evaluate whether CR on its own or in combination with tDCS can be a clinically relevant addition to further enhance recovery. In case the results indicate that cognitive performance can be improved with CR, and whether or not tDCS will lead to additional improvement, this pilot trial will be extended to a large randomized multicenter study. Trial registration Dutch Trial Registry NL7954. Prospectively registered on August 12, 2019.