Mental Capacity in Prader-Willi Syndrome

The Mental Capacity Act (MCA) protects individuals’ rights to make decisions. However, for those with Prader-Willi Syndrome (PWS), especially regarding food and finances, the MCA can present challenges.


PWS involves a biological drive to eat excessively and difficulties with impulse control and risk awareness. Although individuals may understand risks intellectually, neurological factors often impair their ability to regulate behaviours that threaten their health and safety. Similarly, someone may appear to have the capacity to manage finances, but PWS involves compulsive or risky spending, especially around food.


Because the MCA focuses on cognitive understanding, it may not fully address these behavioural complexities. Professionals must therefore balance respecting autonomy with safeguarding wellbeing.


There have been multiple cases of people with PWS dying from overeating shortly after they were deemed to have mental capacity around food and money. 


As well as dying from obesity-related complications, people with PWS can and do die from gastric rupture following a single binge eating episode, even if they are not obese.


  • Research and real world case studies have clearly evidenced that people with Prader-Willi Syndrome do not have capacity to make safe decisions about food and finances.
  • To allow someone with PWS to have free access to food and/or money is a serious safeguarding risk.
Sarah Brindle, PWSA Mental Capacity Lead

Sarah Brindle: PWSA Mental Capacity Lead

Sarah is our resident expert in mental capacity, and can provide advice and support  to professionals and families caring for those with PWS.

Sarah can support you by:  

  • Attending care reviews & meetings
  • Advising on mental capacity assessments
  • Writing letters of support 
  • Advising on LPAs
  • Helping with Continuing Health Care Assessments

About Sarah

  • Sarah is a highly experienced professional with over 20 years of practice in mental capacity, health, and advocacy. 
  • Her expertise includes the Mental Capacity Act 2005, Mental Health Act 1983, associated Codes of Practice, the Human Rights Act 1998,  complex case management including serious medical treatment, DNACPRs, and advance care planning. 
  • Sarah's worked extensively in direct advocacy under IMCA, IMHA, DoLS, and Care Act frameworks, legal literacy in Court of Protection proceedings (e.g., s21A, s16, COP1–COP24) and holds the IMHA and IMCA Level 4 Qualifications.


The Mental Capacity Act: Guidance for Supporting People with PWS

PWS affects decision-making, particularly regarding eating behaviour and diet.

While individuals with PWS can make decisions, their capacity may fluctuate, necessitating supervision and environmental controls.
The following recommendations are taken from "The Mental Capacity Act: Supporting People with PWS"

  • Making Decisions About Food and PWS

    Research highlights the risks associated with uncontrolled access to food for individuals with PWS, emphasizing the need for a food-managed environment to prevent significant weight gain and associated health issues.

  • Legal and Ethical Considerations

    Interventions in a person's autonomy must be justified by law, necessary, and proportionate. This aligns with Article 8 of the Human Rights Act, ensuring respect for private life while addressing the risks posed by unmanaged overeating in PWS.

  • Managing Eating Disorders in Children with PWS

    For children, parents or guardians have a duty under the Children Act (1989) to act in their best interests, including managing the eating environment. If a child is 'Gillick competent,' they may consent to aspects of their care and treatment.

  • Care and Treatment Options for Adults with PWS

    Adults with PWS need a food-managed environment. Support can be provided through:

    1. Consent to Restrictions: Adults who understand the risks and voluntarily agree to supervision or environmental controls.

    2. Mental Capacity Assessments: If an adult cannot consent due to a 'disability of the brain or mind,' the MCA allows others to make decisions in their best interests, ensuring any restrictions are necessary and proportionate.

    3. Other Legislation: The Mental Health Act is less relevant unless severe mental health issues are involved.


  • Assessing Capacity

    Capacity must be assessed for specific decisions at specific times. Individuals with PWS may need detailed capacity assessments, especially if their decision-making ability is inconsistent or if they refuse support.

  • Decision-Making Capacity

    Information on PWS, the risks of unmanaged eating, and available support should be provided to help individuals make informed decisions. Capacity assessments must distinguish between understanding information in theory (decisional capacity) and applying it in practice (executive capacity).

  • Restraints and Restrictions

    Support for individuals with PWS may involve restraints or restrictions to limit unsupervised eating. Such interventions must comply with Section 6 of the MCA, ensuring they are justified and necessary to prevent harm.