Abstract
The TransTheoretical Model (TTM), Self-Determination Theory (SDT), and the Integral Model of Treatment Motivation (IM) provide distinct but not incompatible conceptualisations of motivation. We discuss the utility of these theories as a basis for the improvement of psychiatric treatment engagement and treatment outcomes in patients with severe mental illness. It appears that all three theories have gained support for their predictions of outcomes in patients with severe mental illness, but important questions remain unanswered, such as which of these theories provides the best prediction of treatment engagement and treatment outcomes. We explain how these three theories could complete each other, based on their strong and unique assets. It is imperative that the theories are empirically tested and compared to confirm their utility, and to this end we propose several important research questions that should be addressed in future research. Theory comparisons can advance what is currently known about intrapersonal changes and interpersonal differences in treatment engagement and outcomes in severely mentally ill patients.
Keywords: Motivation, self-determination, transtheoretical, theory, treatment, precontemplation, reinforcement management, schizophrenia, MET, TTM
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