Multidimensional moderators of treatment trajectories in people with schizophrenia at high risk of relapse: findings from a real-world lower middle-income country cohort.

Depression in later life is a major source of suffering and excess disability, with pooled population-based surveys placing the prevalence of clinically significant depressive symptoms at approximately 35.1% (95% CI 30.2%–40.4%) among community-dwelling adults aged 60 years and older (Cai et al., ). The Global Burden of Disease Study 2021 documented a substantial and rising global burden of late-life depression, with marked inequities across countries and sociodemographic strata and a heavier burden in women than in men (Sun et al., ), and the broader 2019 study reported a global rise in mental disorder disability‑adjusted life years (DALYs) from 80.8 million in 1990 to 125.3 million in 2019 (GBD, Mental Disorders Collaborators, 2022). Late-life depression is closely associated with functional decline, social withdrawal, and elevated mortality. Although it has historically been studied as an individual-level disorder, depressive symptoms in older adults are deeply embedded in the marital relationship. Married and cohabiting partners show systematic similarities in depressive symptoms, a phenomenon termed spousal concordance (Meyler, Stimpson, & Peek, ), and recent large-scale evidence indicates that having a depressed partner substantially elevates an older adult’s own risk of depression (Han et al., ). These observations have motivated growing interest in late-life depression as a fundamentally dyadic phenomenon (Kiecolt-Glaser & Wilson, ). Three mechanisms have been proposed to account for spousal concordance in depressive symptoms: assortative mating on shared dispositional and socioeconomic characteristics (Horwitz, Balbona, Paulich, & Keller, ); cumulative joint exposure to common environments and life stressors; and dynamic interpersonal influence on mood through empathy, daily interaction, and emotional contagion. A factor that operates within all three is physical functioning. At the individual level, depressive symptoms predict subsequent decline in activities of daily living (ADL) and instrumental ADL (IADL) (Penninx et al., ), and the reverse direction has been documented in large Chinese longitudinal cohorts (Liu et al., ; Zhou, Wang, & Ma, ; Zhu et al., ). Whether this individual-level bidirectional pattern persists in a dyadic specification that partials out stable between-couple similarity, however, remains to be tested. Within couples, one partner’s functional decline can also increase caregiving demands on the other, a mechanism formalized by the stress-process model as a contributor to elevated depressive symptoms in the caregiving spouse (Pearlin, Mullan, Semple, & Skaff, ). The magnitude of spousal interdependence may vary across cultural contexts. China, the United States, and England offer informative contrasts in family structure and caregiving norms: spouses are the principal caregivers of disabled older adults in the United States and Europe, whereas adult children continue to provide most long-term care in China (Pinquart & Sörensen, ). One of the few harmonized cross-national comparisons of older couples to date reported stronger spousal concordance in depressive symptoms in China than in the United States or England (Lu & Shelley, ); a recent three-cohort analysis of China Health and Retirement Longitudinal Study (CHARLS), Health and Retirement Study (HRS), and SHARE similarly found that adverse-childhood-experience–depression spousal concordance is stronger in China than in Western settings (Sun et al., ). Most existing dyadic studies of late-life depression have relied on the actor–partner interdependence model (APIM), which does not separate stable between-couple similarity from prospective within-person change (Cook & Kenny, ; Hamaker, Kuiper, & Grasman, ; Kenny, Kashy, & Cook, ). A two-wave APIM analysis of 1,245 spousal caregiving dyads in CHARLS (Liu et al., ) reported gender-asymmetric partner effects, but its generalizability beyond a Chinese caregiving subsample remains untested. Recent extensions of the random-intercept cross-lagged panel model to dyadic data (Mund, Park, & Nestler, ) provide a means to disentangle between-couple stability from prospective within-person change in mixed-sex couples, but applications to late-life depression across socioculturally distinct cohorts remain scarce. Whether the prospective coupling between depressive symptoms and functional limitations operates consistently within and across spouses in different sociocultural settings, and whether observed concordance reflects dynamic interpersonal influence or stable shared characteristics, therefore remains unresolved.