The overall purpose of this thesis is to increase knowledge of the concept of functional capacity and how it is related to everyday functioning for adult patients with schizophrenia spectrum disorders. The thesis comprises three papers (Papers I-III) based on empirical data from a clinically representative sample of outpatients. The results in the first study (Paper I) indicated that the Swedish version of University of California San Diego Performance-based Skills Assessment-Brief (UPSA-B) is a reliable instrument, with good psychometric properties in terms of both validity and reliability. UPSA-B is a performance-based instrument used to assess functional capacity, i.e. the patient’s ability to perform certain everyday tasks, necessary for independent functioning, in a controlled setting. In the second study (Paper II), the aim was to investigate if and how demographic variables and illness activities, together with functional capacity, contribute to predicting real-world functioning milestones. Functional capacity was mainly associated with education level and housing situation. In the third study (Paper III), the aim was to investigate how the patient's self-rating ability regarding functional performance relates to neurocognitive performance and real-world functional performance. The results showed that 37% of patients overestimate their functional performance. The results also showed that clinicians seem to have greater difficulty assessing patients who overestimate their functioning. In summary, this thesis states that using UPSA-B to measure functional capacity offers considerable advantages and plays an important role in capturing functional outcomes. The importance of taking control of limited self-rating ability in patients with schizophrenic spectrum disorders is also demonstrated.

The overall purpose of this thesis is to increase knowledge about the concept of functional capacity and the way it is related to everyday functioning for adult patients with schizophrenia spectrum disorders. UCSD Performance-based Skill Assessment-Brief (UPSA-B) is a performance based instrument used to assess functional capacity, the patient’s ability to perform certain everyday tasks in a controlled setting. The result in Paper I indicated that the Swedish version of UPSA-B is a reliable instrument with good psychometric properties. The aim in Paper II was to investigate if and how, demographic variables and illness activities together with functional capacity contribute to predict real-world functioning milestones. Functional capacity was mainly associated with education level and housing situation. In Paper III the aim was to investigate how the patient's self-rating ability regarding functional performance relates to neurocognitive performance and real-world functional performance. The results showed that 37 % of patients overestimate their ability of functional performance. In sum, this thesis states that using UPSA-B to measure functional capacity has great advantages and plays an important role in capturing functional outcomes.