Improving functioning in severe mental illness with cognitive remediation: study protocol for a pragmatic randomised multi-centre trial with adjunct sham-controlled tDCS (HEADDSET+)

Individuals with severe mental illness (SMI) face daily challenges, often due to cognitive impairments. While cognitive remediation (CR) can improve both cognitive and functional outcomes, especially when combined with other rehabilitation interventions, its effectiveness in individuals with SMI requiring sheltered housing remains unclear. This trial primarily investigates whether CR improves daily and cognitive functioning compared to a waitlist period. As a second exploratory aim, we will examine whether adding transcranial direct current stimulation (tDCS) enhances the effectiveness of CR in a randomised sham-controlled comparison. Lastly, the trial examines participants’ subjective experiences of the CR intervention. We hypothesise improvements in goal attainment, daily functioning, and cognition. Using a non-concurrent multiple baseline design, 126 participants (aged 18–65) with SMI residing in sheltered housing facilities will receive 16–20 weeks of twice-weekly CR sessions lasting 30–45 min, combined with either active (N = 63) or sham tDCS (N = 63). Functional, cognitive, and clinical assessments will be conducted at baseline, post-waitlist, post-treatment, and 6-month follow-up. Additionally, participants’ meta-cognitive skills and subjective experiences will be evaluated post-treatment. In multilevel mixed models, we will evaluate the effect of CR (combining both CR groups) vs. waitlist, and compare CR + active tDCS vs. CR + sham tDCS to explore potential augmentation effects. If effective, integrating CR, with or without tDCS, into standard care may benefit recovery in individuals with SMI requiring long-term support. ClinicalTrials.gov: NCT06378463, registered on April 17, 2024.