Subthreshold depression (StD) is considered a precursor stage of major depressive disorder (MDD) and represents an important target for early intervention [1]. It is typically characterized by the presence of 2-4 depressive symptoms persisting for at least 2 weeks without meeting the full diagnostic criteria for MDD [2]. Epidemiological studies suggest that StD is highly prevalent in the general population, with estimated rates ranging from 7.3% to 17.2% among adults, and is associated with a significantly increased risk of developing MDD and other psychiatric disorders [3]. In addition, individuals with StD may experience impaired functioning and an elevated risk of suicidal ideation [4]. Therefore, early and effective interventions targeting StD are essential to prevent the progression to MDD and to reduce associated public health burdens.

Exercise therapy is a proven nonpharmacological intervention for reducing depressive symptoms, offering advantages such as low cost, few side effects, and rapid efficacy [5]. However, its repetitive and unengaging nature often limits motivation and long-term adherence. Given that depression is characterized by low mood and diminished interest in activities [6], interventions that incorporate behavioral activation and intrinsic motivation are particularly suitable.

In recent years, serious games, digital games designed for purposes beyond entertainment, such as education, rehabilitation, or health promotion, have increasingly been explored as innovative tools for behavioral and mental health interventions [7]. Within this broader category, exergames represent a specific type of serious game that combines physical activity with interactive gameplay and may help overcome some of the limitations of traditional exercise interventions [8]. During exergaming activities, participants are more likely to experience a state of flow, which has been associated with greater enjoyment and sustained engagement in physical activity [9,10].

Through game mechanics such as goal-oriented tasks, real-time feedback, and reward structures, exergames have emerged as a promising approach for enhancing enjoyment, intrinsic motivation, and adherence to physical activity programs while simultaneously delivering therapeutic benefits. Previous studies have shown that exergames not only facilitate light-to-moderate intensity exercise but also enhance users’ self-efficacy and willingness to engage in physical activity [11], thereby improving adherence [12]. These features may be particularly relevant for individuals with StD, who often exhibit reduced behavioral activation and altered reward sensitivity [13].

Nintendo Switch, featuring somatosensory controls and immersive design, has shown high safety, feasibility, and user satisfaction across health contexts [14,15], and is increasingly applied in neurorehabilitation and mental health care. Studies have shown that Nintendo Switch–based exergames improve physical [16,17] and psychological outcomes across populations [18-21]. Furthermore, the qualitative studies have also shown their feasibility and acceptability among stroke survivors [22] and older adults [23], who reported positive experiences and social enjoyment.

Despite the growing body of research on exergaming interventions, most studies have primarily focused on older adults [18,19] or specific clinical populations [20,21]. Evidence specifically targeting adults with StD remains limited. Moreover, most existing studies have primarily focused on quantitative outcomes, while participants’ subjective experiences and perceptions of exergame-based interventions remain underexplored. Understanding both the effectiveness and user experience of such interventions may provide important insights for optimizing digital mental health strategies.

Therefore, this study, conducted based on a previously published protocol [24], was designed as a mixed methods exergaming effectiveness trial to evaluate a Nintendo Switch–based exergaming intervention using Ring Fit Adventure (RFA; Nintendo Co Ltd) as the intervention platform. The study aimed to: (1) evaluate the effectiveness of a Nintendo Switch–based exergaming intervention in improving depressive symptoms, anxiety symptoms, and sleep quality among adults with StD; and (2) explore participants’ subjective experiences of the intervention, including engagement, perceived benefits, and acceptability.

This mixed methods sequential explanatory design comprised an assessor-blinded, parallel-group randomized controlled trial (RCT) and semistructured qualitative interviews to evaluate the effectiveness of Nintendo Switch–based exergaming in adults with StD. This RCT adhered to the CONSORT (Consolidated Standards of Reporting Trials) 2025 statement (Checklist 1) and the CONSORT-EHEALTH (Consolidated Standards of Reporting Trials of Electronic and Mobile Health Applications and Online Telehealth) extension for electronic and mobile health interventions to enhance transparency and reproducibility of reporting (Checklist 2) [25,26]. The qualitative component followed the APA Journal Article Reporting Standards for Qualitative Research (JARS-Qual; Checklist 3) [27].

No patient or public involvement was incorporated into the design, conduct, reporting, or dissemination of this research.

The protocol registered in the trial registry differed from the final study protocol in several aspects. First, the sample size was provisionally estimated as 50 participants in total (25 per group) based on previous studies at the time of trial registration. Prior to participant recruitment, a meta-analysis of available studies on exergame-based exercise training for depressive symptoms in adults was conducted to obtain a more precise estimate of the expected effect size [28]. Based on the pooled effect size (0.69), the required sample size was recalculated, resulting in a revised target of 38 participants per group. Second, in the trial registry, StD was defined by the Center for Epidemiologic Studies Depression Scale (CES-D) ≥16 and a 24-item Hamilton Depression Rating Scale (HAMD-24) score between 8 and 20. Prior to recruitment, this criterion was refined to align with contemporary diagnostic practice. In the final protocol, StD was defined as CES-D≥16 in individuals not meeting DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition) diagnostic criteria for MDD. Third, the trial registry included several additional secondary outcomes (eg, subjective experience, flow experience, physical training, sports motivation, exercise intensity, and BMI). The present report focuses on the primary outcome (depressive symptoms) and 2 secondary outcomes (anxiety symptoms and sleep quality), while the remaining registered outcomes will be reported separately.

Ethical approval was obtained from the Clinical Research Ethics Committee of the School of Nursing, Jilin University (Ref: 2022091401). The study protocol has been published previously [24], providing detailed information on the study design, target population, intervention procedures, and planned data analyses. All study procedures complied with the principles of the Declaration of Helsinki and relevant ethical guidelines for research involving human participants. Written informed consent was obtained from all participants prior to enrollment. To protect participant privacy, all data were deidentified immediately after collection and stored using anonymous identification codes. All analyses were conducted using these coded identifiers, and no personally identifiable information is included in this manuscript or any supplementary materials. Participants who completed the full study protocol, including assessments at T0, T1, T2, and T3, received small gifts after each assessment as appreciation for their participation. Participants who completed all assessments and intervention sessions received an additional gift package valued at approximately Renminbi (RMB) 200, equivalent to approximately US $30.

Figure 2 shows the recruitment and assessment process. Between January and February 2023, eligibility assessments were conducted on 183 potential participants. Of these, 99 individuals were excluded, including 63 who did not meet the inclusion criteria and 36 who declined to participate. A total of 84 eligible participants were randomly assigned in a 1:1 ratio to either the IG (n=42) or the control group (CG; n=42). During the follow-up period, 3/42 (7.1%) participants in the CG discontinued participation at T1 due to illness (n=1), scheduling conflicts with class time (n=1), and loss of interest (n=1). No participants in the IG were lost to follow-up. The overall attrition rate was 3/84 (3.6%). To examine the mechanism of missing data, Little’s MCAR test was conducted for variables included in the outcome analyses (PHQ-9, GAD-7, and PSQI scores), which indicated that the missing data were completely at random (χ²₆=3.606; P=.73). Therefore, missing values were handled using the last observation carried forward method under the ITT principle, and all randomized participants (n=84) were included in the final analysis.

The intervention was delivered as planned throughout the 8-week intervention period. A total of 42 participants in the IG received the 8-week Nintendo Switch–based exergaming intervention under the supervision of trained facilitators in the psychological and exercise laboratory setting. All sessions were conducted according to the predefined intervention protocol. Facilitators supervised the exercise sessions, provided technical guidance on the use of the Ring-Con and leg-strap accessories, ensured participant safety, and offered encouragement to support engagement during gameplay. Session attendance and participation were recorded to monitor adherence. Overall, adherence of adults with StD was relatively good; most students (35/42, 83.3%) exceeded 896 minutes of participation time. No adverse event was reported.

Table 1 summarizes the baseline characteristics of the participants. The mean age was 23.07 years (SD 1.45), and 83.3% (70/84) of the participants were female. There was no statistically significant difference between the 2 groups in demographic information and outcome variables (P>.05).

As shown in Table 2, the statistically significant effects of the group×time interaction between the 2 groups were found in PHQ-9 scores (T1: β=−4.07, 95% CI −5.84 to −2.30; P<.001; T2: β=−4.29, 95% CI −6.14 to −2.43, P<.001; T3: β=−3.81, 95% CI −5.54 to −2.08; P<.001). The results of the pairwise contrast tests are shown in Table 3. The IG showed greater significant improvements in PHQ-9 scores at all T1 (mean difference [MD]=−5.48, 95% CI −6.72 to −4.23; P<.001), T2 (MD=−6.10, 95% CI −7.41 to −4.78; P<.001), and T3 (MD=−5.79, 95% CI −7.10 to −0.47; P<.001) compared with the CG. Figure 3A illustrates the temporal trends of depression outcomes, derived from the results of the GEE analyses.

As shown in Table 2, the group×time interaction had a statistically significant effect on PSQI scores at all follow-up points (T1: β=−2.98, 95% CI −4.55 to −1.40; P<.001; T2: β=−2.19, 95% CI −3.58 to −0.80; P=.002; T3: β=−2.45, 95% CI −3.81 to −1.09). Anxiety symptoms also improved significantly at T1 (β=−2.60, 95% CI −4.70 to −0.50; P=.02) and T3 (β=−2.38, 95% CI −4.62 to −0.14; P=.04). For sleep quality in Table 3, the IG showed greater significant improvements in PSQI scores at all T1 (MD=−1.67, 95% CI −2.66 to −0.67; P=.001), T2 (MD=−2.00, 95% CI −2.78 to −1.22; P<.001), and T3 (MD=−2.05, 95% CI −2.81 to −1.28; P<.001) compared with the CG. In terms of anxiety, there was a significant improvement in the IG compared with the CG also at T1 (MD=−3.19, 95% CI −4.54 to −1.84; P<.001), T2 (MD=−3.19, 95% CI −4.54 to −1.84; P<.001), and T3 (MD=−2.24, 95% CI −3.73 to −0.75; P=.003). Figure 3B-3C illustrates the temporal trends in sleep quality and anxiety outcomes.

Seventeen adults with StD participated in the semistructured interviews, including 2 males and 15 females, aged 22-29 years (mean 23.18, SD 1.78). The average duration of the interviews was 26.7 minutes. Details are shown in Multimedia Appendix 4.

Three major themes emerged from the semistructured interviews content analysis. The corresponding codes and representative quotations are presented in Table 4. Figure 4 presents the thematic map that shows the relationships among the themes, categories, and codes identified in the qualitative analysis. To protect confidentiality and preserve anonymity, participant quotations are followed by their participant number (P_n).

This study evaluated the effectiveness of a Nintendo Switch–based exergaming program for adults with StD using a mixed methods design. The results showed that participants who engaged in the exergaming program experienced significant improvements in depressive symptoms and sleep quality, along with reductions in anxiety symptoms, compared with the CG. The qualitative findings further complemented the quantitative results by providing deeper insights into participants’ experiences with the exergaming intervention. Participants described immersive engagement during gameplay, perceived psychophysiological benefits, and multiple facilitators and barriers influencing adherence (eg, game-related, individual-level, and environmental factors), which helped contextualize the observed improvements in depressive symptoms, anxiety symptoms, and sleep quality.

Our findings indicate that the 8-week Nintendo Switch–based exergaming intervention significantly improved depressive symptoms among adults with StD, with improvements maintained at both 4-week and 8-week follow-up assessments. Consistent with previous literature, regular physical activity has been widely recognized as an effective nonpharmacological strategy for improving depressive symptoms [39]. These benefits may be partly explained by biological mechanisms whereby exercise promotes neuroplasticity and neurogenesis through the regulation of neurotrophic factors and modulates the synthesis and release of key neurotransmitters involved in mood regulation [40]. In addition to these physiological mechanisms, exercise may also contribute to mood improvement through behavioral and psychological pathways, including behavioral activation, improved sleep, and enhanced psychological well-being [40]. However, traditional exercise programs often face challenges related to low motivation and poor long-term adherence, particularly among individuals experiencing depressive symptoms [41].

Exergames, as a specific type of serious game that integrates physical activity with interactive gameplay, may help address these challenges by enhancing engagement and motivation [8]. From the perspective of behavioral activation theory [42], individuals with StD often experience reduced activity levels and diminished exposure to rewarding experiences [43]. Exergames such as Ring Fit Adventure provide structured, goal-oriented tasks, real-time feedback, and reward systems that encourage participants to re-engage in meaningful and rewarding activities [44]. Through repeated participation, these mechanisms may help break cycles of avoidance and inactivity and promote behavioral activation [45]. In addition, several design features of exergames may further contribute to their psychological benefits [46]. As reflected in participants’ postintervention interviews, game elements such as progressive game design and personalization, feedback-driven engagement, and gamified incentive structures may enhance users’ self-efficacy and perceived competence. According to social cognitive theory, higher self-efficacy is an important determinant of sustained behavioral engagement [47]. At the same time, gamified reward structures and immersive gameplay may increase enjoyment and intrinsic motivation, thereby promoting sustained participation in physical activity [48]. This mechanism was further reflected in participants’ feedback; for example, one participant noted that “the level-based challenges, points, and mini-games gave me a real sense of enjoyment and competition,” highlighting how game-based elements can transform exercise into a more engaging and motivating experience.

The present findings differ from those reported by Wu et al [16], who reported less favorable mood-related outcomes following a 4-week Ring Fit Adventure intervention in university students. One possible explanation is intervention duration. Longer intervention periods may provide more time for participants to establish regular engagement and benefit from repeated behavioral reinforcement [49], thereby supporting more stable behavioral and emotional change, consistent with behavior change theory [50]. This interpretation is also consistent with our previous meta-analysis, which suggested that longer-duration exergame interventions were associated with greater improvements in depressive symptoms [28]. Another possible explanation relates to differences in sample characteristics. The present study included a higher proportion of female participants. Previous research has suggested that women may demonstrate higher adherence to structured health programs, which could influence intervention outcomes [51]. Therefore, the gender composition of the sample may have partly contributed to the more favorable results observed in the present study.

A slight rebound in depressive symptoms was observed at the T2 and T3 follow-up stage. One possible explanation is that the beneficial effects of the intervention gradually attenuated after the withdrawal of structured guidance and routine participation. In addition, the later follow-up period overlapped with examination periods for many students, which may have increased academic stress and negatively affected mental health [52].

Although the group×time result for GAD-7 was not statistically significant, pairwise comparisons revealed significantly greater anxiety reductions in the IG at all time points. This suggests that Nintendo Switch–based exergaming may still exert beneficial effects. The finding is broadly consistent with a prior study [53]. One possible explanation lies in the differential sensitivity of anxiety to behavioral activation. While both anxiety and depression involve disrupted emotional regulation, anxiety is often more reactive to acute stressors and environmental uncertainty [54]. Exergames may contribute to anxiety reduction by providing structured physical routines, immersive attentional distraction, and rhythmic motor engagement [55].

The study also suggested that exergaming intervention showed potential to improve sleep quality, although a previous study using a similar intervention did not report statistically significant effects [16]. These improvements may reflect both psychological and physiological pathways. Psychologically, reductions in depressive symptoms, anxiety, and stress may indirectly contribute to better sleep [56,57]. Physiologically, exergaming may support sleep through mechanisms related to thermoregulation, autonomic function, and overall physical activation [58,59]. In addition, qualitative findings suggested that participants experienced relaxation and enhanced well-being during the intervention, which may also have contributed to improved sleep.

The study demonstrated high adherence and no adverse events, indicating the intervention’s safety and feasibility. This strong engagement was likely supported by both the design features of the exergame and the structured implementation context [46]. On the one hand, game elements such as interactive feedback, clear goals, progressive challenges, and an engaging narrative may have enhanced participants’ motivation and enjoyment [44]. On the other hand, the intervention was delivered in a structured laboratory environment with scheduled sessions, facilitator supervision, and regular support from the research team, which likely further promoted adherence and sustained participation [60]. Accordingly, the observed effects may reflect the combined influence of both game design and human support.

This study has several limitations. First, the sample consisted exclusively of university students, whose stress patterns, sleep routines, and lifestyle characteristics may differ from those of the broader adult population, particularly during examination periods, thus limiting the generalizability of the findings. Second, the intervention was delivered in a structured laboratory environment with scheduled sessions and facilitator supervision. Although this likely supported adherence and intervention fidelity, it differs from the typical home-based use of Ring Fit Adventure. Therefore, caution is needed when generalizing the findings to less controlled real-world settings. Third, the IG and CG differed in the degree of structure and contact with the research team. Participants in the IG received supervised sessions and regular support, whereas the CG continued usual activities without comparable contact. As such, some of the observed effects may have been influenced not only by the exergaming intervention itself but also by differences in attention and support. Fourth, because the intervention combined both game-based design features and facilitator support, it was not possible to fully disentangle the relative contributions of human scaffolding and game design to the observed outcomes. This distinction is important for understanding the scalability of the intervention in less supported settings. Fifth, the follow-up period was limited to 8 weeks. As such, the long-term sustainability of the observed improvements in depressive symptoms and sleep quality remains uncertain. Future studies with extended follow-up periods are warranted to determine whether these benefits persist over time. Sixth, due to the nature of the intervention, blinding of participants and intervention providers was not feasible. This may have introduced potential performance or expectancy biases, as participants aware of receiving the intervention might have reported greater improvements [61]. However, outcome assessors and data analysts were blinded to group allocation to minimize potential bias. Future studies could further strengthen methodological rigor by incorporating additional objective outcome measures.

This study makes several contributions to the exergame literature. First, it extends the evidence by focusing specifically on adults with StD, a population at elevated risk of developing MDD but underrepresented in exergaming research. In contrast to many previous studies that have primarily targeted older adults or specific clinical populations, the present study examined the potential of exergaming as an early preventive intervention for adults with StD. Second, this study was designed as a mixed methods exergame effectiveness trial, combining longitudinal outcome evaluation with qualitative inquiry. This approach not only assessed whether the intervention was beneficial but also provided insight into how participants experienced the program and which factors influenced engagement and adherence. Third, the findings contribute to the broader exergames for mental health field by showing how design features such as progressive challenges, feedback, and gamified incentives may support behavioral activation, self-efficacy, and sustained participation. Finally, from a practical perspective, the study suggests that commercially available exergaming platforms such as Nintendo Switch–based exergaming intervention offer a feasible, engaging, and potentially scalable digital strategy for supporting mental health and sleep outcomes in adults with StD.

This study identified the positive effects of an 8-week Nintendo Switch–based exergaming intervention in improving depressive symptoms, anxiety, and sleep quality among adults with StD. Qualitative findings further revealed that immersive engagement, perceived psychophysiological benefits, and multifaceted adherence facilitators ranging from gameplay design to individual and environmental factors played a key role in sustaining participation and enhancing intervention effectiveness. Together, these findings suggest that gamified physical activity may represent a feasible and engaging approach for promoting mental well-being in adults with StD. By integrating interactive gameplay with exercise, commercially available exergaming platforms may offer a promising and accessible strategy for early mental health support in real-world settings.