DISCUSSION
5‐years‐3‐months
This RCT examined the longitudinal effects of the MC following responder couples through two or three MCs across more than 5 years. In brief, these couples who had benefitted from two previous MCs showed maintenance of small to medium effects on two out of four outcome measures (MSI and ISQ) at 4 years and 9 months. Hereafter, the changes in couples who received a third MC were not significantly different than the changes in couples who only received the first two MCs. Across the period of the third MC, within‐group analyses revealed that while couples in the current control group showed flat trajectories, couples receiving a third MC experienced small to medium within‐group booster effects on three out of four measures (MSI, CSI, and RAS) with one measure (MSI) maintaining a small to medium effect at the 5‐years‐3‐months follow‐up. Generally, these boosts around the third MC repeat the climbing M pattern of trajectory seen in couples receiving the two previous MCs (Cordova et al., Couples receiving a third MC showed small positive anticipation effects on two outcomes, similar to findings from the original RCT. Potential explanations for these anticipation effects could be out‐of‐session mechanisms such as relationship reappraisal, behavioral activation, and motivation from social control and social desirability (see also Trillingsgaard et al., Generally, we found that the within‐group effects of the third MC were not as large as those of the second MC. This contradicts our initial expectation of One measure of relationship satisfaction (MSI) showed generally stronger maintenance of effects than the other measure (CSI), which could be explained by characteristics of the two measures. Item response theory‐based examination of the MSI has found it to discriminate distressed couples particularly well (Balderrama‐Durbin et al., It follows from our selection of a responder sample that our results cannot generalize to the full population. Though the recurring MCs seemed like a beneficial dose and type of help for the current responder couples, this may not generalize to the nonresponder couples. Based on panel plots of the 2‐year trajectories in the 19 nonresponder couples excluded from this study, they were characterized by being either (a) constantly distressed throughout the period with no or close to no response to the two MCs, (b) responding positively to the MCs but quickly dropping down to their baseline, or (c) constantly satisfied. From the perspective of both cost‐effective and ethical delivery of help, the adequacy and necessity of the MC will depend on the individual couple's need and response. For distressed couples who do not respond to the first MC, this intervention is best conceptualized as an important steppingstone toward more intensive interventions tailored to their specific needs.Finally, findings should be interpreted in light of some limitations. First, this study was short of power to detect statistical significances of small effects, thereby including a risk of a type II error. The current effect sizes (e.g., the between‐group effects of 0.33 and 0.31 found in the MSI) call for future replications with larger samples to detect potential between‐group effects with a power of at least 0.80. As the MC is a brief intervention offered to couples across the continuum of distress, small effects may represent meaningful benefits in a public health perspective. Second, our design did not allow us to attribute any of the effects to mechanisms of change specifically linked to the MC. Studies comparing the MC to another intervention or studies specifically designed to disentangle mechanisms of change are needed for that purpose.