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Development and psychometric properties of the Psychological Therapies Outcome Scale – Intellectual Disabilities (PTOS‐ID)
Author(s) -
Vlissides N.,
Beail N.,
Jackson T.,
Williams K.,
Golding L.
Publication year - 2017
Publication title -
journal of intellectual disability research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.941
H-Index - 104
eISSN - 1365-2788
pISSN - 0964-2633
DOI - 10.1111/jir.12361
Subject(s) - psychology , clinical psychology , intellectual disability , construct validity , exploratory factor analysis , concurrent validity , scale (ratio) , distress , anxiety , mood , psychometrics , reliability (semiconductor) , anger , psychiatry , internal consistency , power (physics) , physics , quantum mechanics
Background There are few valid and reliable psychological therapy outcome measures available for use with people with intellectual disabilities (ID). The current study involved the development of a new scale; the Psychological Therapies Outcome Scale – Intellectual Disabilities (PTOS‐ID), and the examination of its validity and internal consistency. Method The PTOS‐ID was administered to 175 people who have ID accessing specialist ID services. The construct validity of the scale was investigated through exploratory factor analysis, concurrent validity through comparison with the Brief Symptom Inventory and internal reliability through internal consistency analysis. Results Three factors emerged from the principal components analysis with high levels of internal consistency: (1) anger and mood (α = 0.82); (2) positive well‐being (α = 0.81); and (3) anxiety (α = 0.76). Factors (1) and (2) were combined to measure psychological distress (α = 0.85), which correlated strongly with the Global Severity Index of the Brief Symptom Inventory ( r = 0.85). Conclusions This preliminary study suggests that the PTOS‐ID is a psychometrically robust measure of psychological distress and psychological well‐being that can be used with people with ID. Further research is required to assess its reliability and ability to detect change.