A Network Model of Health-Related Changes after a Lifestyle-Enhancing Treatment in Patients with Severe Mental Illness: the MULTI Study VI

Abstract

Background/objective: The effects of lifestyle interventions on physical and mental health in people with severe mental illness (SMI) are promising, but its underlying mechanisms remain unsolved. This study aims to examine changes in health-related outcomes after a lifestyle intervention, distinguishing between direct and indirect effects.

Method: We applied network intervention analysis on data from the 18-month cohort Multidisciplinary Lifestyle enhancing Treatment for Inpatients with SMI (MULTI) study in 106 subjects (62% male, mean age=54.7 (SD=10.8)) that evaluated changes in actigraphy-measured physical activity, metabolic health, psychopathology, psychosocial functioning, quality of life and medication use after MULTI (n=65) compared to treatment as usual (n=41).

Results: MULTI is directly connected to decreased negative symptoms and psychotropic medication dosage, and improved physical activity and psychosocial functioning, suggesting a unique and direct association between MULTI and the different outcome domains. Secondly, we identified associations between outcomes within the same domain (e.g., metabolic health) and between the domains (e.g., metabolic health and social functioning), suggesting potential indirect effects of MULTI.

Conclusions: This novel network approach shows that MULTI has direct and indirect associations with various health-related outcomes. These insights contribute to the development of effective treatment strategies in people with severe mental illness.

Keywords: Schizophrenia; physical activity; physical health; psychosocial functioning; quality of life.

Fig. 1

Scores of physical and mental health-related outcomes on baseline (T1) and 18-month follow-up (T2) in MULTI (n=65) and TAU (n=41). Significant differences between change scores are marked (* p<.0045, Bonferroni corrected). Note. Pmed, psychotropic medication; Smed, somatic medication; TAC, total activity counts (actigraphy measure for total physical activity); Pos, positive symptoms; Neg, negative symptoms; Soc, Health of the Nation Outcome Scale (higher scores indicate poorer social functioning); WQOL, WHO Quality of Life Brief Questionnaire; EQ5D, EuroQol 5D; Abd, abdominal girth; MAP, mean arterial pressure; Chol, total cholesterol.

Fig. 2

Estimated network for the multidisciplinary life-style intervention (MULTI) in relation to mental and physical health-related changes (n=106). Circular nodes represent change scores in the outcome variables, triangular nodes represent baseline variables, and the rectangular node represents the treatment allocation variable. Edges represent conditional dependence relationships between the variables; blue edges represent positive associations, whereas red edges represent negative associations. The thickness and saturation of the edge is proportional to the strength of the association. MULTI is directly related to a decrease of Neg, Pmed, Abd, Soc and an increase of TAC, and a slight increase of Pos. Note. *Higher scores on Soc indicate poorer social functioning.