Research shows that people with severe learning disabilities get depressed at least as often as the wider population. Psychological therapies are recommended to treat depression, and some of these have been adapted for those people with learning disabilities who can talk about their problems. No research has properly tested a psychological therapy for people with severe learning disabilities and any mental health problem. The investigators recently completed a study that tested a psychological therapy (behavioural activation) for people with mild learning disabilities and depression. Behavioural activation improves people's mood by helping them to re-engage in activity that has meaning and purpose for them, rather than relying on talking or thinking skills. Because of this behavioural activation might be promising for people with severe learning disabilities and depression. Along with PAMIS, an organisation for families of people with more profound disabilities, the investigators have adapted the therapy for this group. The investigators now want to find out if it would be possible to carry out a research project about whether behavioural activation works for depressed adults with severe learning disabilities. This is called a feasibility study. The investigators would see if it is possible to recruit 50 adults with severe learning disabilities, and if they are willing to be randomly placed in a group who get behavioural activation or a group who get usual help from services. Other information about running a study would be collected, including about keeping in contact with participants and what measures are needed to find out if change is happening.

People with severe and profound learning disabilities have significant lifelong impairment of general intelligence (IQ<40 with associated adaptive skill deficits). They have high support needs and limited or no verbal communication.

Prevalence of depression is increasing for people with learning disabilities (from 12.6% in 2016/17 to 14.5% in 2021/22 in England). The main treatment in use is medication, and antidepressant use is rising.

The 2016 NICE guideline on mental health problems in people with learning disabilities found the only available evidence on psychological interventions for depression was very low quality for specially adapted Cognitive Behavioural Therapy (CBT), and only for people with mild/moderate learning disabilities. Only three RCTs (total n=130) and three controlled before-and-after studies (total n=130) of CBT were identified for all mental health conditions. There was no evidence for people with severe learning disabilities, and CBT is not accessible to people with significant communication and cognitive limitations. The NICE included research recommendations for psychosocial intervention RCTs for people with severe learning disabilities and mental health problems.

Behavioural Activation (BA) uses behavioural principles to treat depression and is probably more accessible to people with severe learning disabilities than wholly talking therapies like CBT. The core aims of BA are: i) to reduce general avoidance of activity, commonly associated with depression, and ii) to increase engagement in valued and purposeful activity. In the general population, BA is at least as effective as antidepressant medications and superior or non-inferior to CBT, pill-placebo, and treatment as usual; and has effects as lasting as CBT following treatment termination.

The investigators aim to examine the feasibility of completing a two arm RCT of an adapted version of behavioural activation for people with severe to profound intellectual disabilities (BeatIt2), with participants randomised to BeatIt2 alongside treatment as usual (TAU) or to TAU alone.

Research questions concern: i) recruitment, ii) retention 12 months post-randomisation, iii) outcome measures with greatest utility in detecting meaningful change, and iv) whether adverse events occur.

A process evaluation will also be carried out, bringing together evidence on: v) acceptability of the intervention across families, paid carers and services, vi) fidelity of therapy delivery and adherence to the manual, vii) feasibility of collecting service use and quality of life data from adults with severe learning disabilities from both arms of the study (to test the feasibility of a later health economic study), and viii) the mechanisms of change and how the context of the intervention affects implementation.

Inclusion Criteria:

• Administratively defined severe/profound learning disabilities, confirmed by carer report using the Vineland Adaptive Behaviour Scales 3rd edition. A severe/profound learning disability will be confirmed by an ABC composite score of 50 or below (Sparrow et al., 2016). Individuals with severe/profound learning disabilities can be characterised by high support needs, limited or no expressive or receptive verbal communication, and significant impairments across adaptive functioning skills.
• 18 years old and over
• Clinically significant unipolar depression, meeting the Diagnostic Criteria for Psychiatric Disorders for use with Adults with Learning Disabilities
• Has a family member or paid carer who has supported them for a minimum of 6 months to complete the screening and baseline visits OR is able to obtain information for the previous 4 months prior to randomisation. The carer, or another named individual, should be available for weekly-fortnightly treatment sessions with the practitioner, and should currently provide a minimum of 10 hours support per week to the participant.

Exclusion Criteria:

• Mild/moderate learning disabilities
• A presentation judged by the research team as likely to interfere with the successful engagement with the intervention (e.g. severe agitation, late-stage dementia, uncontrolled epilepsy).

The research assistants carrying out the assessments will be masked to intervention allocated and/or received. Masking will be maintained using a wide range of procedures, including separate offices for the therapists and research assistants carrying out assessments (where they are located in the same building), protocols for answering telephones, message taking and secretarial support, separate diaries, pigeonholes and data file security, and using passwords and encryption of randomisation information.