Establishment of effective, efficient, and evidence-based interventions in rehabilitation of working memory (WM) deficits after acquired brain injury (ABI) is sorely needed. Despite robust evidence for the usefulness of clinical hypnosis in a wide range of clinical conditions, and improved understanding of mechanisms underlying it ́s effects, the potential of clinical hypnosis in cognitive rehabilitation is virtually unexplored. The current study seeks to replicate resent intriguing findings where large effects of hypnotic suggestion were seen on WM capacity following ABI, and further, explore underlying mechanisms of change.

The potential impact of applying hypnosis in cognitive rehabilitation is substantial. Deficits in WM is one of the most common challenges after ABI and plays a critical role in post-injury outcome. Still, state-of-the-art approaches within WM rehabilitation have not been able to produce significant effects that transfer to real- life functioning for the affected patients. Building on the strong results of hypnosis on WM in ABI from a Danish single trial, we will aim at replication and expansion of the study in a Norwegian context. The initial study will be expanded in terms of number of participants, injury-characteristics will be included, outcome measures of relevance to real-life functioning, and underlying mechanisms of change will be explored. Self-efficacy is generalizable by nature (self-efficacy gained from mastery experiences in one situation generalizes to others), thus WM rehabilitation effects are expected to generalize and transfer to other domains in daily life.

This randomized controlled trial (RCT) aims to evaluate the effectiveness of hypnosis in WM rehabilitation in ABI patients. Ninety patients will be recruited from Sunnaas Rehabilitation Hospital. Inclusion criteria are non-progressive ABI, minimum 12 months post- injury, ongoing WM deficits and age between 18 and 67 years. Patients will be randomized to either a) an intervention group receiving four weekly 60 min. sessions with induction and hypnosis, b) an active control group receiving four weekly 60 min. sessions of induction and mindfulness, or c) a passive control group without intervention. The targeted procedure consists of suggestions about enhancing WM functions through the instantiation of preinjury WM ability in the present using age regression and visualizations of brain plasticity. The non- targeted suggestions contain no explicit mentioning of ABI or WM-related abilities. Each participant will be assessed at baseline, immediately after intervention and six months after baseline. Primary outcome is WM as measured by neuropsychological tests as well as self- and informant reported WM capacity. Secondary outcomes include self-rated ABI related symptoms, self-efficacy, mental health, and global outcome. A process evaluation will be carried out to evaluate treatment experience,

Rehabilitation of impaired WM after ABI has hitherto yielded limited clinical effects, and clinical trials of new interventions are thus warranted. Long-standing empirical evidence demonstrates that hypnosis is an effective therapeutic technique in a wide range of conditions, including in altering cognitive functions and improving WM in healthy adults, supported by imaging data. Recent exploratory research has suggested remarkable efficacy of hypnosis in improving WM in patients with ABI. However, these findings need replication in studies applying scientifically rigorous designs. If successful, our ambition is to provide recommendations and materials to implement hypnotic suggestion as an adjunct treatment following ABI in Norwegian rehabilitation clinics. Study findings may inform future studies exploring the use of clinical hypnosis in other areas of rehabilitation, such as mild TBI, and in other neurological conditions where WM deficit is prominent.

Inclusion Criteria:

• A documented non-progressive ABI, minimum 12 months post- injury and ongoing WM deficits by self-report and/or neuropsychological assessment
• The above mentioned patients have received multidisciplinary cognitive rehabilitation before participation

Exclusion Criteria:

• Patients with severe mental illness
• Patients progressive neurologic disease
• Patients with ongoing ICD-10 diagnosis of substance dependence
• Patients that lack Norwegian language skills

It is not possible to blind participants or therapists to group allocation during the intervention. Independent Outcome Assessor(s) will be blinded to group allocation. Participants will be provided with new IDs in final database, blinding researchers to which group is the interventions group, active control group or passive control group during analysis.