Intellectual disability and mental health

A team from the Cope Foundation looks at the challenges involved in the management of mental health conditions in the ID population and describes a course designed to upskill nurses working in this area

Ms Siobhan Kirby, RNID, Cope Foundation, Cork, Mr Dave Quinlan, ANP Positive Behavioural Support, Cope Foundation, Cork and Mr Sam Lake, Behaviour Support Therapist, Cope Foundation, Cork

September 1, 2023

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  • Four in every 10 people with an intellectual disability (ID) experience a mental illness in their lifetime.1 The World Health Organization (WHO) describes mental illness as “a clinically significant disturbance in an individual’s cognition, emotional regulation or behaviour… usually associated with distress or impairment in important areas of functioning”.2

    The ID supplement to The Irish Longitudinal Study on Ageing (IDS-TILDA) report stated that mental health and emotional problems were greater among those with ID than among the rest of the population and were increasing in prevalence.

    From an Irish perspective, more than half of the participants (52%) in the IDS-TILDA Wave 3 study reported a diagnosis of a mental health disorder, with anxiety and depression identified as most prevalent.3

    This article explores the mental health issues that are specific to people with an ID and describes a training course developed at the Cope Foundation in Cork for nurses supporting adults with an ID.

    Risk factors for mental illness

    The vulnerability of people with an ID is complex, with various overlapping risk factors that can be categorised as follows: 

    • Biological – syndrome related (eg. Fragile X syndrome, Prader-Willi syndrome), health (eg. epilepsy), pain, sensory issues

    • Social – living conditions, poor socialisation and limitations in adaptive behaviour, lack of employment and meaningful roles

    • Psychological – stressful life events, lack of self-esteem, difficulty accessing appropriate services.

    Mental health presentations

    The presentation of mental health conditions in people with ID can be typical or atypical. Clinical presentation can be influenced by a person’s level of ID and communication difficulties. People with milder ID and good verbal communication skills are usually able to describe what they are experiencing and often present in a manner familiar to most mental health professionals.

    Atypical presentation is usually evident in those with severe ID or in people with communication difficulties. This can mean that mental illnesses mainly present as behaviours that are problematic for the person or their support system. Therefore, individuals showing behavioural changes require careful assessment for a range of potential contributing factors, including underlying mental or physical health conditions.4

    Diagnosis of mental illness

    In considering the vulnerability of this population, diagnosis of mental illness is important to ensure:

    • Evidence-based treatment, eg. unipolar depression versus bipolar depression

    • Prognosis, eg. Alzheimer’s in people with Down syndrome

    • Insight, eg. behavioural phenotypes presenting with autism

    • Access to resources and benefits.

    Despite the importance of diagnosis, there are no conclusive tests for mental illness in the ID population (other than for some dementias and encephalopathies), therefore history taking, self reports and observations are essential to the diagnostic process.

    The most frequently used mental illness assessment tools include the Diagnostic Manual-Intellectual Disability 2 (DM-ID2), International Classification of Diseases (ICD-11) and the Diagnostic and Statistical Manual of Mental Disorders fifth edition (DSM-V).

    Barriers to diagnosis

    Challenges to diagnosis include communication barriers, overlapping symptoms and comorbidities. Because of these barriers, diagnostic overshadowing can occur. This happens when a healthcare professional decides that what a person with ID is experiencing with their mental or physical health is because of their ID and not because they are having an additional mental health issue.

    Treatment options

    Treatment options available to those with an ID and mental illness should be tailored to the individual’s mental health presentation. Mental health support and interventions can include medications, positive behaviour support, mindfulness and cognitive behavioural therapy (CBT). Treatment approaches are multifactorial and often incorporate interdisciplinary collaboration, eg. nursing, occupational therapy, speech and language therapy, psychology, psychiatry, behaviour therapy, social work, physiotherapy, dietetics and other complementary therapies. 

    Role of the nurse

    Nurses have a key role in supporting people with an ID who are experiencing mental illness. Their role involves:

    • Contributing to the diagnostic process

    • Co-ordinating and collaborating with relevant stakeholders

    • Implementing evidence-based clinical supports and interventions

    • Evaluating the effectiveness of treatment plans.5

    Identification of education needs

    Following a training needs analysis report commissioned by the NMPDU in 2020 – ‘Education and Training Needs of Registered Nurses Intellectual Disability and Registered Psychiatric Nurses in Cork and Kerry’ – it was identified that there was a need for training in mental health and ID.6

    A one-day course for nurses supporting adults with ID was developed by staff at the Cope Foundation in collaboration with staff from external services. The course is titled ‘The Impact of Mental Ill Health on People with Intellectual Disability’ and has received NMBI Category-1 approval for seven CEUs.

    Participants who attended the inaugural course in April evaluated the course positively and reported the following:

    • “The course increased my understanding of mental health among people with ID”

    • “The course was relevant to my role as a nurse”

    • “I will be able to apply the theory that I learned on the course to my nursing role.”

    It is anticipated that the course will be offered biannually and will be evaluated and updated on an ongoing basis. 


    1. Cooper SA, Smiley E, Morrison J, Allan L, Williamson A (2007) Prevalence of and associations with mental ill-health in adults with intellectual disabilities. British Journal of Psychiatry. 190 27–35. doi: 10.1192/bjp.bp.106.022483
    2. World Health Organisation (2022) Mental Health: Factsheet Geneva: World Health Organization Mental disorders ( (accessed June 2023) 
    3. McCarron M, Cleary E, and McCallion P (2017) Health and health-care utilization of the older population of Ireland: comparing the intellectual disability population and the general population. Research on Aging 39(6) 693-718
    4. HSE (2021) Mental Health Services for Adults with Intellectual Disabilities: National Model of Service, Dublin, Health Service Executive
    5. Sheerin F, Fleming S, Burke E et al (2019) Exploring mental health issues in people with an intellectual disability. Learning Disability Practice. doi: 10.7748/ldp.2019.e1999
    6. Nursing and Midwifery Planning and Development Unit, HSE South Cork/Kerry (2020) Education and Training Needs of Registered Nurses Intellectual Disability and Registered Psychiatric Nurses in Cork and Kerry Education and Training Needs of Registered Nurses Intellectual Disability and Registered Psychiatric Nurses in Cork and Kerry 2020 ( (accessed May 2023) 
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