Investigating Psychological Symptoms and Patient Report Outcome Measures (PROMs) for People with Intellectual Disabilities: Validating and Abbreviating the Outcomes and Wellbeing Distress Scale for Adults with ID (OWLS-ID)

Individuals with intellectual disabilities (ID) are more likely to experience common mental health problems, including depression. As such, understanding the factors related to depression in this population is important to inform assessment and treatment. Psychological therapies are a recommended approach to treating depression. Patient reported outcome measures (PROMs) are tools which can assess symptoms and evaluate psychological therapies.
Part I of this thesis identified factors in the literature which are associated with depression in populations with ID. Research in depression and ID is significantly less than that of the general population. The literature often debates whether depression presents differently in this clinical group. As such, it would be helpful to understand what factors are associated with depression to support the development of targeted interventions. Part I also considered which PROMs were used to measure depressive symptoms in these studies. This highlighted a wide range of measures, few of which were specifically developed for those with ID.
Part II investigated the reliability and validity of an existing measure of psychological distress in people with ID, the Psychological Therapies Outcome Scale–ID (PTOS-ID-II). The measure was made specifically for this population and has been used in many clinical and research settings. However, its validity and reliability had yet to be examined in its current form. Validation analysis identified two items that were unnecessary and subsequently removed. Overall, 27-items remained which showed evidence of reliability and validity. This new measure was named ‘Outcomes for Wellbeing and Distress Scale’ (OWLS-ID). Part II then considered the feasibility of creating a shorter version of this measure for quick administration in practice. A 10-item version of the measure was created which also showed evidence of reliability and validity. This was named the OWLS-Mini.