Introduction

Until recently, research has focused on factors that hinder well-being, with the objective of identifying means by which to ease suffering [1]. Over the last fifteen years, however, many psychology researchers have insisted on the necessity to extend these studies by analyzing the individual differences and the processes that contribute to well-being [2]. One objective of this latter research is to highlight individuals' available means to boost their subjective happiness. According to Duckworth, Steen, and Seligman [3], these means are threefold: increasing pleasure, boosting engagement, and finding meaning in life. As pleasure is the fruit of experiencing positive emotions, increasing their frequency, intensity, or duration is one of the avenues through which individuals can achieve higher levels of happiness [4]. Indeed, a growing number of cross-sectional, longitudinal, and experimental studies show that positive emotions play a key role in individuals' evaluation of their level of well-being and contribute to numerous related benefits (for a review, see [5]). For example, at the cognitive level, experimental studies have shown that inducing positive emotions broadens individuals' scope of attention [6] and increases their creativity [7]. At the somatic level, longitudinal studies have shown that positive emotions are associated with increased longevity [5], [8]–[11], which is not surprising, as experience of positive affect was associated with better immunity in cross-sectional [12], [13] and experimental studies [14], [15]. At the social level, positive affect is related to better interpersonal relationships [16]–[20] and generally increases altruism [21], [22]. As a whole, these studies point to the importance of positive affect at both the individual and the societal levels and highlight the importance of developing interventions aimed at increasing positive affect and, consequently, well-being.

To provide clinicians with practical and efficient interventions, researchers have created and validated a set of techniques that enable individuals to increase their positive emotions and their levels of well-being (for a review, see [23]). In this area of research, techniques were frequently tested one at a time and presented to participants as one-shot exercises. This way of proceeding enables researchers to test the efficacy of each exercise individually. However, recent research [24] has shown that this way of testing interventions has low ecological validity because, in naturalistic settings, happiness seekers often practice (and wish to practice) multiple exercises at the same time. Furthermore, the use of multiple techniques in an intervention often produces better results than when a single technique is used alone [24].

Several authors have tested interventions aimed at consolidating multiple techniques, provided as either individual or group sessions (e.g. [25]–[27]). Criteria used to determine a technique's inclusion in those programs were not always clearly defined or explicitly reported. In the 1980s, Fordyce [25], [26] gathered a set of exercises aimed at teaching happiness seekers to mimic typical behaviors and thinking styles of happy people. The exercises included in Fordyce's program encouraged participants to: (a) keep busy and be more active; (b) spend more time socializing; (c) be productive at meaningful work; (d) get better organized and plan things out; (e) stop worrying; (f) lower expectations and aspirations; (g) develop positive, optimistic thinking; (h) become present-oriented; (i) work on a healthy personality; (j) develop an outgoing, social personality; (k) be yourself; (1) eliminate negative feelings and problems; (m) see close relationships as the number one source of happiness; (n) put happiness as your most important priority ([26], p.484). In a more recent attempt, Seligman, Rashid, and Parks [27] created a program gathering the “best-documented exercises” in the literature ([27], p. 776) targeting at least one of the three components of “happiness,” as defined by Seligman (i.e., positive emotions, engagement, and meaning) [4]. Exercises integrated in Group Positive Psychotherapy were the following: (a) using your strengths; (b) three good things/blessings; (c) obituary/biography; (d) gratitude visit; (e) active/constructive responding; and (f) savoring ([27], p. 776).

Although these studies provided essential information about the potential of integrative interventions, this kind of program would greatly benefit from a strong theoretical background which should (1) at a theoretical level, allow a better understanding of the mechanisms underlying happiness enhancement and (2) at a more practical level, help practitioners identify their clients' needs, weaknesses, and the most appropriate technique(s) to prescribe them [28]. As no happiness enhancing program that is both integrative and theory-driven currently exists, we decided to create such a program and to evaluate its effects on a set of mental and physical health variables. To this end, we developed an integrative program structured around a conceptual framework, which enabled us (1) to select a set of techniques involving different underlying processes and (2) to organize them in a coherent manner.

The model proposed by Quoidbach et al. [28], [29] appears to fulfill these requirements. As outlined below, Quoidbach et al. modeled positive emotion regulation strategies with reference to a well-known model in the domain of negative emotion regulation: Gross' Process Model of Emotion Regulation [30], [31]. This model enables the integration of strategies involving clearly differentiated emotion regulation processes and the reconciliation of studies on both positive and negative emotion regulation.

The Process Model of Emotion Regulation applied to Positive Emotions

The Process Model of Emotion Regulation [30], [31] provides a theoretical structure for analyzing emotion regulation processes. The model highlights five families of emotion regulation strategies. Initially created to understand and organize negative emotion regulation strategies, it was later adapted by Quoidbach et al. to apply to the up-regulation of positive emotions (see The Process Model of Positive Emotion Regulation, Quoidbach et al. [28], [29]). The first family of strategies that can be used to influence emotion is situation selection. Situation selection involves “choosing or avoiding some activities, people, or places in order to regulate emotions” [32]. To illustrate this strategy, we can imagine a grandfather, Joseph, deciding to visit his children and grandchildren on Sunday afternoon because he knows that being in touch with his family gives him a lot of pleasure.

The second family of strategies highlighted by Gross, situation modification, includes techniques that allow an individual to change the situation s/he is facing (or that s/he has planned) in order to change its emotional impact. To continue our example, in order to make Sunday afternoon fun and enjoyable, Joseph may decide to bring his grandchildren’ favorite board game that they all like to play together.

Attentional deployment includes strategies that involve altering how an individual feels by selecting the information to which s/he attends. During Sunday afternoon, rather than getting irritated by the noise of the neighbor's lawnmower, Joseph may fully focus his attention on the fun game he is playing with his grandchildren. Along the same line, Joseph may concentrate his attention on the taste of the wonderful cheesecake his daughter prepared and deeply savor it to get the most pleasure from it.

Cognitive change refers to changing the way an individual thinks in order to change the way he/she feels, either by changing how he/she thinks about the situation itself or about his/her capacity to manage its demands. For instance, rather than taking the moment for granted, Joseph may interpret his presence among his family that afternoon as a gift of life.

Finally, the last family of strategies proposed by Gross is response modulation. This family of strategies involves techniques to alter bodily manifestations of emotion (e.g. physiological, behavioral). In order to increase his excitement and pleasure during the time he is spending with his family, Joseph may decide to smile and laugh with his loved ones and to express his affection for them.

Given that generating a high level of well-being implies reminiscing about past positive events, savoring the present, and anticipating positive future events [33], [34], [35], Quoidbach et al. [28], [29] divided Gross's model into three moments of action: before, during, and after the positive emotions generating event (for a detailed description of the model, see [28], [29]). Thus, Quoidbach et al. [28], [29] do not propose five large families of strategies, but rather 15 distinct strategies that an individual can use to regulate his/her emotions, corresponding to the 15 sections of the Process Model of Positive Emotion Regulation (see Table 1, see italics).

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Table 1. Example of positive emotion regulation techniques in the Positive Emotion Regulation Model proposed by Quoidbach & al. [28], [29] for a specific positive event.

https://doi.org/10.1371/journal.pone.0095677.t001

The use of such a framework makes it possible to classify the different types of techniques that individuals may use to maximize their positive emotions. Table 1 illustrates a positive event and the means an individual may use to increase the intensity, frequency, and duration of the positive emotions that s/he experiences. Each action (or technique) that an individual can implement in order to up-regulate his/her positive emotions with respect to a given positive event finds its place in one of the model's sections. As this model enables the integration and organization of happiness enhancing techniques, it offers an interesting framework with which to elaborate our intervention.

The Current Study

The aim of the present study was twofold: (1) to create an integrative intervention (i.e. including multiples techniques) on the basis of a theoretical model and (2) to evaluate its impact on psychological and physical well-being variables.

First Objective: Creation of the Positive Emotion Regulation (PER) Program

To achieve our first objective, we carried out an extensive literature review on the basis of the model proposed by Quoidbach et al. [28], [29] in order to identify a set of validated happiness enhancing techniques that we could include in our intervention. For each technique, we identified at which moment of action it was applicable (i.e., before, during, and/or after an event). We then evaluated the family of strategies to which each of these techniques corresponded. By combining this information, we were able to identify the strategy (or section) of the model to which each technique corresponded. This theoretical framework provided us with a structure in which to organize these validated techniques within an integrative intervention seeking to regulate positive emotions and to increase individuals' well-being.

This selection and classification process led us to include the following techniques in our intervention (see Table 2 for a detailed overview of the PER program, the extensive manual is available upon request from the first author). Techniques in the situation selection section aim at teaching people the kind of events they should plan (see B1 in Table 2, corresponding to “Before an event”), experience (see D1 in Table 2, “During an event”), or remember (see A1 in Table 2, “After an event”) in order to increase their level of well-being. These techniques included the following: playing sports [36], being altruistic [37], socializing [38], taking care of one's needs [39], goal setting [40], monitoring progress toward a goal [41], and identifying memories to preserve [42] or to recall [43].

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Table 2. Week-by-Week Summary of the Positive Emotional Regulation Program.

https://doi.org/10.1371/journal.pone.0095677.t002

Techniques in the situation modification section aim to modify planned (B2) or current (D2) activities, or their memories of these activities (A2), in order to optimize their well-being potential. Techniques such as time management and planning [44], job crafting [45], optimizing the end of an event [46], finding the flow [47], and showcasing souvenirs [48] were included in this category.

Attentional deployment techniques help individuals to project themselves into a pleasant future (B3), to be fully present in an agreeable moment (D3), or to relive happy or meaningful moments of their lives (A3). Exercises such as imagining your best future self [49], mental time traveling to a pleasant future [50], savoring [51], and mental time traveling into past positive events [52] are examples of techniques in this category.

Techniques identified as cognitive change strategies aim at helping individuals to interpret future (B4), current (D4), and past events (A4) in a positive way and to make individuals aware of the good things in their lives. This category of techniques includes optimistic thinking [53], reducing one's expectations [54], counting one's blessings [55], counterfactual thinking [56], writing a gratitude letter [57], and what-went-well exercises [58].

Finally, in the response modulation category, we gathered techniques used to facilitate positive emotion expression for future (B1), current (D5), and past events (A5). Included exercises are sharing excitement for upcoming events [59], smiling [60], sharing good news with others [61], capitalizing [62], and gratitude visits [63].

Results

Preliminary results.

Dropout analysis revealed that among the 36 participants assigned to the PER group, four of them left the program before its end (11% of the subjects). Among the 35 participants assigned to the LKM condition, 15 of them withdrew before the end ( =  43%). A Chi-square test revealed that the dropout difference between the two groups was significant, X² (1, N = 71) = 9.125; p<0.003. No differences between subjects who dropped out and those who did not were found on the variables under study at T1, according to t-test analyses (ps ranging from.486 to.967).

A one-way analysis of variance (ANOVA) was performed to check for potential group differences at T1 between completers of the three groups (see Table 3 for the values). This analysis indicated that there were no significant baseline differences between groups on any of the following variables: subjective happiness, life satisfaction, depression, perceived stress, somatic complaints, and age (ps ranging from.247 to.935). Difference in sex ratios among the three groups was nonsignificant, according to a Fisher's exact test conducted on the number of remaining males and females after dropout among each group (p = .268).

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Table 3. Means (and Standard Deviations) for Each Scale and Each Group and Significance of Differences Between Time 1 and Time 2 for PER and control group.

https://doi.org/10.1371/journal.pone.0095677.t003

Test of our hypothesis.

In order to assess the evolution of participants' scores within each group, we computed change scores by subtracting T1 scores from T2 scores for each participant on each variable. A graphic depiction of mean change scores (expressed in percent) by group can be found in Figure 1.

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Figure 1. Mean Change Scores (expressed in percent) between Time 1 and Time 2 for the three groups.

ΔSHS  =  Mean Change Score on Subjective Happiness Scale; ΔSWLS  =  Mean Change Score on Satisfaction With Life Scale; ΔBDI  =  Mean Change Score on Beck Depression Inventory; ΔPSS  =  Mean Change Score on Perceived Stress Scale; ΔPILL  =  Mean Change Score on Physical Inventory of Limbic Languidness.

https://doi.org/10.1371/journal.pone.0095677.g001

Separate one-way ANOVAs with one between-subject factor (three groups: PER, LKM, and control) were then performed on change scores in order to compare the three groups. Analyses showed that the mean difference score for SHS tended to be greater in LKM and PER than in the control group. The effect was only marginally significant (p = 0.08) but the power was low (P = 50%). The mean difference score for BDI tended to also be greater in LKM and PER than in the control group. Again, the effect was only marginally significant (p = 0.09) but the power was low (P = 48%). The mean differences for SWLS and for PSS were not statistically different between groups (ps = .24 and 0.11, respectively), but the power of the analyses was again very low (P = 31% and 44% respectively). Finally, the mean difference score for PILL was statistically different between groups (p =  0.018, P = 73%): the control group differed significantly from LKM (p = 0.044) and marginally from PER (p = 0.065).

Although these results are somewhat informative, the very low powers of the analyses are problematic. Statistical power can be interpreted as the probability of finding a significant difference, if it exists, with the present sample sizes and the observed effect sizes. The conclusion that can be drawn from those results is that, for our effects to be statistically significant, we would need a much larger sample size. When power analyses are used to determine the optimal size of a sample before the beginning of a study, standards recommend powers between 80 to 95% [77]. Though the power of our study was far from this standard, this was a pilot study, and as such, we were unable to predict (1) the dropout rate in each group, and therefore the adequate number of participants to initially include in our study, and (2) the average effect size of our intervention, which would have been necessary to compute power analyses before the start of the study.

The high dropout rate in the LKM group dramatically reduced the number of observations and, therefore, considerably reduced the power of analyses including all three groups. Under these conditions, it seems hardly possible to highlight results on the PER group, even though the visual analysis of the change scores (see Fig 1) suggests that some interesting results do exist.

Since the power problems were mainly related to the LKM group, and since our main group of interest was the PER group, we decided to leave the question of LKM efficacy aside, so as to focus on our main question of interest: the efficacy of the PER program. Analyzing those results independently of the LKM seemed to constitute the most relevant option (from both a clinical and statistical point of view) to quantify the effects of the PER intervention, if they exist. In the following pages, we will present the results of analyses comparing the PER and control groups only. The means and standard deviations for each variable at each time point in the PER program and in the control group are shown in Table 3.

Repeated measures ANOVAs were performed on each measure, with group (PER program, control) as a between-subjects factor, and time (T1, T2) as a within-subjects factor. In each case, we were looking for a significant Time x Group interaction, which would indicate a differential change between the two groups. Analyses confirmed a highly significant group interaction for four of the five scales: SHS, F(1, 59) = 5.52, p<.022, η²_partial = .09; SWLS, F_{(1, 60)} = 4.20, p<.045, η²_partial = .07; BDI, F_{(1, 60)} = 4.50, p<.038, η²_partial = .07; and PILL, F_(1,59) = 5.86, p<.021, η²_partial = .09. Results for PSS did not reach significance (F_{(1, 59)} = 2.99, p = .089, η²_partial = .05).

As depicted in Table 3, the breakdown of these interactions revealed that, unlike participants in the control group, who did not show any change on any variable under study between T1 and T2, participants in the PER group showed a significant increase in subjective happiness (SHS), t (26) = −2.94, p>.007, d = .50, and satisfaction with life (SWLS), t (27) = −2.88, p<.008, d = .51. They also showed a significant decrease in depression (BDI), t (27) = 2.73, p<.011, d = .61 and physical symptoms (PILL), t (26) = 3.30, p<.003, d = .51 and a marginal decrease in perceived stress (PSS), t (27) = 1.97, p = .059, d = .38 (see Table 3).

Discussion

The objective of our study was twofold: (1) to construct a theory- and evidence-based integrative intervention aimed at increasing well-being and (2) to test its effectiveness on participants' mental and physical well-being. Based on the Process Model of Positive Emotion Regulation [28], [29], we developed a 12 hour (6 × 2 hr) integrative training program, bringing together a series of theory-based and empirically-validated techniques. The theoretical framework allowed us to organize these different well-being enhancing techniques and to deliver them in a coherent format. In addition, this framework made it possible to integrate techniques using different underlying processes (or strategies).

In accordance with our hypothesis, our results indicate that, compared to an inactive control group, the PER group showed a significant increase in subjective happiness and satisfaction with life and a significant decrease in depression symptoms and somatic complaints. There was also a marginal decrease in perceived stress. These results confirm that it is possible to enhance an individual's psychological and physical well-being and that the PER program that we developed is a valid intervention to achieve this goal.

Another interesting finding of our study concerns loving-kindness meditation. In our study, the LKM dropout rate (43%) suggests that, although LKM seems to work for those who follow the program until the end, a significant proportion of participants do not adhere to this intervention. It is worth noting that the high dropout rate in the LKM condition is consistent with results reported by Carson et al. [78]. The latter study tested the effects of LKM among chronic pain sufferers and also showed a 42% dropout rate (13 out of 31 subjects) in its LKM group. However, individuals who fully adhered to the intervention until the end of the program benefited from it, as evinced by better psychological adjustment to pain. Several hypotheses can be put forward in order to explain the high dropout in our study. First, participants who enrolled in our program had no precise idea of the type of techniques they were going to learn, unlike in Fredrickson et al.'s [65] well-known LKM study, where participants enrolled in a “meditation program.” It is therefore possible that some of them were surprised by the proposed method and found that it did not suit them, which may have caused them to drop out of the intervention. The majority of the qualitative feedback received from participants who quitted the LKM condition mentions an incongruity between the proposed technique and their personality (e.g. “I am too impatient for this type of exercise,” “Meditation stresses me, I am not comfortable with this type of method,” “If I had known that we were going to meditate, I would not have signed up”). Second, another explanation that may explain the high dropout rate in the LKM group concerns the trainers [79]. As pointed by an anonymous reviewer, the large number of dropouts could have been because some participants did not enjoy the personality of the trainer and/or the type of group dynamic he proposed. In order to reduce the risk of having such a trainer effect, we recruited two LKM trainers. Results indicate that the observed dropout was independent of the trainer identity. For this reason, we believe that this second hypothesis is less plausible.

Overall, our results and previous literature suggest that LKM can be an effective technique to increase the well-being of individuals who adhere to the program. Our results also show that the PER program is an effective alternative that may be more readily accepted by the majority of individuals. Previous LKM results (e.g. [65], [78]) suggest that it may be interesting to include elements of LKM within an integrative intervention such as the PER program, or to recommend this technique to individuals for whom this type of intervention appears to be the most clinically relevant (e.g. people open to meditative practices).

In addition to bringing a theoretical reflection about the processes underlying happiness enhancing techniques, this article aimed to provide practical information to practitioners desiring to use an integrative and theory-driven intervention to boost their clients' well-being. This is why we have described the PER program that we developed based on Quoidbach et al.'s theoretical model [28], [29] in greater detail than usually found in empirical articles. Like one anonymous reviewer, one may wonder whether the underlying theoretical model must be described to the participants. Based on our experience and on participants' qualitative comments at the end of the sessions, we think that it should definitely be explained to them. First, several times during the training, we invite participants to choose the exercises they wish to practice from a selection that we offer (for their weekly homework and long-term exercises after the end of the program). However, the techniques that individuals prefer are not always those that are best for them [69], [80]. Explaining the model to the participants therefore seems important, so as to show them the variety of techniques available and to encourage them to try at least one technique from each type of strategy (or model section) in order to discover new methods to enhance their happiness level. Second, some of our participants reported that the classification of strategies made them aware that they always use the same family of strategies and rarely any of the others. For instance, one participant realized that he often interprets events positively (cognitive level), but that he is systematically incapable of being fully present during the pleasant moments he experiences (attentional level). Other participants reported similar realizations about techniques usable before, during or after an event. One young woman clearly identified that she is able to feel a lot of positive emotions about past events, but that she almost never plans future events in order to get the most out of them. Thus, the model increases participants' awareness of their functioning and provides them with new ways to increase their well-being. We therefore encourage trainers who would like to teach the PER program to present and explain the model to their groups.

In individual therapy, Quoidbach et al.'s model [28], [29] could also be used to identify strategies that a happiness seeker has not been using, and thereby the type of exercise(s) that could be prescribed. However, further research should be conducted to better understand which strategies are the most beneficial for specific profiles of individuals. Pending the development of individually tailored happiness enhancing interventions (see [57], [81] for examples of “tailored interventions” attempts), integrative programs such as the PER program offer the greatest probability of being effective for the widest range of individuals.

Limitations and Future Research

Although this study offers promising prospects, we acknowledge several limitations that leave ample room for future research to refine our findings. The first limitation concerns the missing data in the LKM condition due to the large dropout rate that we had not expected. The number of missing data in this group strongly decreased the statistical power to a point where we did not have sufficient power to demonstrate effects, even if they existed. Now that we have information about the potential dropout rate in the LKM condition, we could run this study again, but this time calculate the appropriate number of participants to include in the groups in order to have a satisfying remaining power at the end of the study, even if a large portion of participants were to fail to complete the intervention.

The second limitation concerns the timing of the assessments. Our post-intervention measure was carried out only once, four weeks after the end of the intervention. Although most of the literature about happiness enhancing strategies includes T2 assessment right after the end of the last exercise, we chose to collect that information four weeks after the end of our intervention because it seemed methodologically more appropriate to measure the remaining impact of our intervention in individuals' real life. Indeed, right after the intervention, people are still fully impregnated with it, while a few weeks later, they have returned to their life, without any reminder of the techniques proposed within the intervention. Although this timing difference diminishes our ability to compare our results to those obtained with other techniques presented in the literature, the fact that we found results four weeks after the end of our intervention shows that it continues to exert its effects after the end of the intervention. It would have been ideal, of course, to follow participants over a longer period of time to be able to do more sophisticated statistical analyses and to see if the benefits maintain in the long term, after six months or one year. Unfortunately, most of our participants were in their last year at university and left the department a few months after the end of the intervention, which led their student email address to be disabled. We lost contact with most of them right after this T2 measurement.

A third potential limitation of our study concerns the composition of our sample. On the one hand, all the participants in our study were young adults, and as a consequence, our results may not be generalizable to the entire population. However, findings from the meta-analysis carried out by Sin and Lyubomirsky [23] indicate that the benefits of positive psychology interventions tend to increase with age. This observation therefore leads us to speculate that testing our intervention on a “young” sample probably resulted in an underestimation, rather than an overestimation, of its effects. On the other hand, our experimental groups were composed of a very limited number of men (PER, N = 4; LKM, N = 3), and this prevented us from investigating a potential impact of gender on the effectiveness of the intervention. It is therefore risky to affirm that our results can be generalized regardless of participant gender. Nevertheless, existing literature in this field has shown no systematic influence of gender on the effectiveness of happiness enhancing techniques, a fact that increases our confidence in the predictive validity of our results for both sexes.

Using only self-reported measures is a fourth limitation of our study. Although numerous authors insist that using self-evaluation is a sensible logical way to evaluate a subjective experience such as well-being [82], we consider that it is necessary to complement these measures with objective health indicators (such as cortisol level [83]), 360 degree assessments (e.g. ratings of one's happiness by friends, partner; frequent verbal expression of positive emotions, [84]) or experience sampling methods [85] in future studies. This kind of measure should decrease the risk of social desirability effects linked to the use of self-report measures and increase the reliability and objectivity of the findings.

As pointed by an anonymous reviewer, future research would benefit from comparing our PER group to existing integrative interventions such as Seligman et al.'s Group Positive Psychotherapy [27]. This would allow determining more precisely the efficiency of our training compared to other integrative intervention and the added value of the theoretical model that underlies it.

Finally, despite the fact that we present an integrative intervention, we acknowledge that studies that focus on specific techniques are critically important. In addition to enabling the evaluation of the unique effect of a particular technique, these studies are crucial in determining the strategies that are particularly beneficial or harmful for specific sub-populations (e.g. highly depressed people, young adults VS people in the final stage of life, individuals from different cultures) and they help understand the processes underlying the effectiveness of a given technique.

Conclusion

Embarking on the path towards higher levels of well-being is a demanding journey that requires motivation and considerable effort [82]. In order to help individuals seeking happiness along this path, this study outlines an intervention that offers clinicians and trainers a variety of techniques that target different processes and structures them around a theoretical framework.

Acknowledgments

We thank Christophe Dierickx, Anaïs Dhaene, Antoine Lecat, Emilie Monnart, Florine Mouillard, Gwennaëlle Rivez and Sophie Snyckers for their help in intervention conception and delivery and/or data collection.