Do partners’ levels of physiological arousal become linked in close relationships? The term “physiological linkage” describes covariation between people in their moment-to-moment physiological states. The current review presents a conceptual framework to guide research on linkage in romantic relationships and discusses the potential implications of being “linked.” Evidence of linkage was found across a broad range of physiological indices and in a variety of contexts, including during laboratory-based conflict and in daily life. Four hypotheses regarding how linkage relates to individual and interpersonal functioning are evaluated: (1) co-activation of the sympathetic nervous system or hypothalamic-pituitary adrenal axis is “bad,” (2) moderate physiological linkage is “just right,” (3) physiological linkage is problematic if the individual or couple is overloaded, and (4) the implications of physiological linkage depend on the emotional context. We found partial support for the first hypothesis and determined that more research is needed to evaluate the remaining hypotheses. Linkage in cortisol was negatively associated with relationship satisfaction; but at the same time, linkage in multiple systems was positively associated with indices of relationship connectedness, such as the amount of time spent together and the ability to identify the emotions of one’s partner. These results suggest that linkage may confer benefits but also may put couples at risk if they become entrenched in patterns of conflict or stress. With research in this area burgeoning in recent years, this review indicates that linkage is a promising construct with applications for interventions targeting individual health and couple functioning.

Using daily diary data, this study examined cross-day associations between family conflict and school problems and tested mediating effects of daily negative mood and moderating effects of psychological symptoms. For 2 weeks, parents and adolescents (N = 106; mean age = 15.4) reported daily conflict; adolescents reported daily negative mood and school problems. Results indicated bidirectional, multi-day spillover between parent-adolescent conflict and school problems with daily negative mood statistically accounting for spillover both within and across days. Externalizing symptoms strengthened links between father-adolescent conflict and school problems, whereas depressive and anxious symptoms strengthened links between parent-adolescent conflict and daily negative mood. By demonstrating cross-domain transmission of daily problems, these findings highlight the salience of everyday events as possible intervention targets.

For many married individuals, the ups and downs of daily life are connected such that stressors impacting one person also impact the other person. For example, stress experienced by one individual may “spill over” to negatively impact marital functioning. This study used both partners’ daily diary data to examine same-day and cross-day links between stress and marital conflict and tested several factors that make couples vulnerable to spillover. Assessment of 25 wide-ranging sources of daily stress included both paid and unpaid work, health issues, financial concerns, and having to make difficult decisions. Results showed that both husbands and wives’ experience of total daily stress were associated with greater same-day marital conflict and that conflict was greater on days both spouses experienced high levels of stress. Evidence of cross-day spillover was found only in those couples with high concurrent marital aggression and in couples where wives reported high family-of-origin aggression. These results highlight both the common, anticipated nature of same-day spillover and the potentially problematic aspects of more prolonged patterns representing failure to recover from stressors that occurred the previous day. The discussion focuses on how reactivity in one life domain puts that individual at risk for generating stress in another life domain and how current marital aggression and family-of-origin aggression are associated with difficulty recovering from stressful events.

The timing (spacing) of assessments is an important component of longitudinal research. The purpose of the present study is to determine methods of timing the collection of longitudinal data that provide better parameter recovery in mixed effects nonlinear growth modeling. A simulation study was conducted, varying function type, as well as the number of measurement occasions, in order to examine the effect of timing on the accuracy and efficiency of parameter estimates. The number of measurement occasions was associated with greater efficiency for all functional forms and was associated with greater accuracy for the intrinsically nonlinear functions. In general, concentrating measurement occasions toward the left or at the extremes was associated with increased efficiency when estimating the intercepts of intrinsically linear functions, and concentrating values where the curvature of the function was greatest generally resulted in the best recovery for intrinsically nonlinear functions. Results from this study can be used in conjunction with theory to improve the design of longitudinal research studies. In addition, an R program is provided for researchers to run customized simulations to identify optimal sampling schedules for their own research.