Objective: Among patients with PD, determine if there is a bidirectional association between severity of somatic & internalizing symptoms over 3 years.

Background: Among people with Parkinson’s Disease (PD), internalizing disorders (i.e. anxiety & depression) are highly prevalent[1], often comorbid[1], & worsen quality of life[2]. While new models of psychopathology (i.e. HiTOP [3]) have emerged in the general population, this perspective is relatively new to PD research. Furthermore, the Hamilton Anxiety & Depression Rating Scales (HAMA/D) -frequently used to examine internalizing symptoms – were not designed for the PD population. Previous work with these scales[4] revealed two factors consistent with literature on internalizing disorders in older adults[5] – somatic & internalizing symptoms [table1].

Method: Participants in the Parkinson’s Disease Biomarker Program[6] with PD & complete data for HAMA/D with at least 3 study visits were included. Longitudinal relationships were examined using a bivariate dual change score modeling framework with maximum likelihood estimator. Total scores for internalizing & somatic subscales [table1] served as observed indicators. Models were constructed with coupling variables which represented interactions between somatic & internalizing factors & were incorporated in a staged fashion. The final model was selected based on a comparison of fit indices, interpretability, & reflection of theory. All analysis conducted in R using the lcsm package[7]. Standardized parameters are presented.

Results: Of 481 participants, 58% were male [table2]. Univariate models of somatic & internalizing symptoms over time demonstrated adequate fit [table3]. The 4 models demonstrated equivalent fit [table4], thus the model with both coupling variables[figure1] was retained. Somatic symptoms in the prior year had a standardized effect of 2.4 on subsequent internalizing symptoms [table5]. Internalizing symptoms at the prior year had a small relative effect (0.3) on subsequent somatic symptoms [table5].

Conclusion: Internalizing & somatic symptom domains influence each other over time, consistent with literature in the general population[5]. Management options for somatic symptoms should be prioritized and monitoring these symptoms may be more important than explicitly recognizable internalizing symptoms such as low mood or expressed feelings of anxiety.

Somatic and Internalizing Scales

Participant Demographic & Clinical Characteristics

Univariate Model Fit Statistics & Parameters

Bivariate Dual Change Score Model Fit Statistics

Final Bivariate Dual Change Score Model Parameters

Figure 1. Schematic of Final Model

References: risk factors and outcome over two years. Int Psychogeriatr, 2012. 24(10): p. 1622-32.
2. Chuquilín-Arista, F., T. Álvarez-Avellón, and M. Menéndez-González, Prevalence of Depression and Anxiety in Parkinson Disease and Impact on Quality of Life: A Community-Based Study in Spain. J Geriatr Psychiatry Neurol, 2020. 33(4): p. 207-213.
3. Conway, C.C., et al., A Hierarchical Taxonomy of Psychopathology Can Transform Mental Health Research. Perspectives on Psychological Science, 2019. 14(3): p. 419-436.
4. DeMarco, E.C., L. Hinyard, and D. Subramaniam. Revisiting the Gold Standard: Exploring Measurement of Internalizing Psychopathology among People with Parkinson’s Disease with the Hamilton Scales. in Health Care Systems Research Network. 2024. Milwaukee, WI.
5. Morin, R.T., et al., Somatic and anxiety symptoms of depression are associated with disability in late life depression. Aging & Mental Health, 2020. 24(8): p. 1225-1228.
6. Rosenthal, L.S., et al., The NINDS Parkinson’s disease biomarkers program. Mov Disord, 2016. 31(6): p. 915-23.
7. Wiedemann, M., et al., lcsm: An R package and tutorial on latent change score modelling [version 1; peer review: 2 approved]. Wellcome Open Research, 2022. 7(149).

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MDS Abstracts - https://www.mdsabstracts.org/abstract/untangling-bidirectional-influences-of-somatic-and-internalizing-symptoms-among-people-with-parkinsons-disease-a-retrospective-cohort-study/