Enhanced cognitive behavioural therapy for suicidality among people with comorbid mental and physical health conditions: study protocol of a pragmatic randomised controlled trial

Suicidal behaviours represent significant public health concerns. People who present with suicidal ideation and/or self-harm are at an increased risk of suicide. The presence of co-existing or comorbid mental and physical health conditions, coupled with neurobiological factors, exacerbates mental health conditions and increases the risk of suicidal behaviours. Psychotherapeutic interventions, including Cognitive Behavioural Therapy, have been considered first line of treatment for several standalone and comorbid populations. However, research into CBT tailored for people at risk of suicide and self-harm while living with mental and physical health comorbidities is lacking. Therefore, this pragmatic trial aims to examine the effectiveness of an enhanced CBT in addition to standard care in reducing suicidal ideation, compared to standard care only. The study will follow a pragmatic randomised controlled trial design. The primary outcome is post-intervention severity of suicidal ideation and secondary outcomes include self-harm behaviours, depression and anxiety, coping, hopelessness, impact of comorbid conditions, and mental well-being. Additionally, blood and salivary samples will be collected to measure biomarkers of inflammation, hypothalamic–pituitary–adrenal (HPA)- axis, neural plasticity, and the tryptophan-kynurenine pathway. Participants will be randomised following stratification and blocking into the intervention and control arm, and the data will be collected at baseline, post-intervention, and a 3-month follow-up. A participant safety plan specific to the project has been developed and will be implemented throughout the study duration. This protocol has been developed following the SPIRIT guidelines. People who live with long-term physical health conditions and co-existing depression, anxiety and distress are at increased risk of suicidal ideation and self-harm. Using a pragmatic randomised controlled trial methodology, the results of this study will contribute to improving our knowledge of implementing an evidence-based CBT intervention on suicidal ideation including self-harm behaviours, psychological state and biological factors. Prospectively registered on ISRCTN, ISRCTN17751649. Registered on 21 August 2024, https://doi.org/10.1186/ISRCTN17751649 .