Acceptance and Commitment Therapy to improve Neuro-Oncology Wellbeing (ACT NOW)

INTERVENTION: The study aims to recruit 72 patients in total over a 12 month period. The researchers and clinical staff at each site will identify eligible participants according to the inclusion and exclusion criteria. Eligible participants will be provided with an age‐appropriate information sheet by the clinical team and researcher who will invite the patient and parent (if desired in over 16‐year‐olds) to participate during their clinical visit. They will also provide an overview of the study and what it entails. Adequate time will be given to families to read the information and decide whether they would like to participate. If those approached decide they would like to participate informed assent will be sought from participants under 16 years old and informed consent from their parents. Informed consent will directly be sought from participants aged 16 and over. All of those recruited will be asked to express interest and consent to taking part in qualitative interviews after their treatment. Up to 15 of those consenting will be approached to take part in interviews where participants can describe their experience of the study and treatment they received. Treatment within the study will involve up to 12 sessions of ACT, each lasting 1 h, delivered weekly over video‐conferencing. Participants will then be randomly placed (1:1 ratio) into one of two groups, either ACT offered either straight away or after a 12‐week wait. Randomisation will be conducted using established randomisation software (https://www.sealedenvelope.com/). Researchers and participants will not be blind to trial arm allocation. Treatment will begin with written and verbal guidance on the use of video‐conferencing software, how to use it safely, and how to ge CONDITION: Psychosocial oncology and survivorship, mental health, psychological wellbeing, young brain tumour survivors, malignant neoplasms of eye, brain and other parts of central nervous system ; Cancer ; Malignant neoplasms of eye, brain and other parts of central nervous system SECONDARY OUTCOME: There are no secondary outcome measures PRIMARY OUTCOME: ; 1. Psychological inflexibility measured using the Acceptance and Action Questionnaire II (AAQ‐II) for 16‐24‐year‐olds and the Avoidance and Fusion Questionnaire for Youth (AFQ‐Y8) for 11‐15‐year‐olds at baseline, 3, 6, 9, and 12 months; 2. Wellbeing measured using the World Health Organisation wellbeing index (WHO‐5) at baseline, 3, 6, 9, and 12 months; and the Outcome Rating Scale at baseline, each treatment session, then at 3, 6, 9, and 12 months; 3. Generalised anxiety measured using the Generalised Anxiety Disorder assessment (GAD‐7) at baseline, 3, 6, 9, and 12 months; 4. Depression measured using the Patient Health Questionnaire (PHQ‐9) at baseline, 3, 6, 9, and 12 months; 5. Quality of life assessed using the Euroqol 5‐dimensions 3‐levels (EQ‐5D‐3L) for 16‐24‐year‐olds and the Euroqol 5‐dimensions youth version (EQ‐5D‐Y) at baseline, 3, 6, 9, and 12 months; 6. Social engagement measured with the Patient‐Reported Outcomes Measurement Information System, Satisfaction with Social Roles and Activities (PROMIS) at baseline, 3, 6, 9, and 12 months; 7. Functioning assessed using the Strengths and Difficulties Questionnaire (SDQ) at baseline, 3, 6, 9, and 12 months; 8. Health service usage measured using the Client Service Receipt Inventory (CSRI) at baseline 3 and 12 months; 9. The credibility of the treatment assessed using the Credibility/Expectancy Questionnaire (CEQ) at baseline and at session 2 of treatment; 10. Patient evaluations of treatment assessed using the Evaluation of Service Questionnaire (ESQ) at 3 months (for those in the immediate treatment arm) or 6 months (for those in the waitlist arm).; INCLUSION CRITERIA: 1. Aged 11 to 24 years 2. Have had a historical primary diagnosis of brain tumour 3. Have stable disease and either off treatment or on low‐intensity treatment 4. Sufficient understanding of English to engage with the intervention (spoken and written), as judged by the assessing clinician 5. Sufficient cognitive, sensory, and speech capabilities to take part in the intervention 6. Oral and written informed consent to participate in the study given by participants (or their parents if under 16) 7. Participants give written assent if under 16 years old 8. Access to the internet and appropriate devices to receive treatment over video‐conferencing (the default modality for delivery). However, face‐to‐face treatment will be offered if internet access or appropriate device use is not possible for participants who are othe