To identify and assess the articles relevant to the review, the research group devised some inclusion/exclusion criteria to choose papers relevant for this review. These criteria regard: publications in peer review journals; focus on love styles distinguished by Lee and exclusion of papers that focused on other love taxonomies; focus on both marital quality/stability and relational dimensions; good quality of the research method and its accurate description in the paper.

In order to identify the studies and research projects relevant to this review, we have used electronic databases such as ScienceDirect, PsycINFO, PubMed, Scopus, and Google Scholar. The most part of the papers were collected from Google Scholar and ScienceDirect. We have considered papers in English and Italian published from 2004 to this day, implementing the meta-analysis proposed by Masuda [22] as a means of synthesis of the research results. Masuda studied the correlation between relational satisfaction and two love types―passionate and companionate―measured by means of various tools applied to the most widespread theories. It was thus a more limited review―in terms of the variables considered―compared to the one presented in this article, but that in any case offered a framework of the state-of-the-art up until the date of its publication, and which supported the difference between Lee’s theory and other theoretical models of love, giving credit to the greater elaboration of the former.

The following key words and key word combinations have been used for this review: love or love style and marital quality, marital stability, marital satisfaction, marital well-being and health.

We have included studies and research projects published from 2004 to 2018 that analyse the love style topic, along with variables in the quality and duration of the relationship. We have excluded the ones that did not involve love styles and relational aspects in their analysis. In any case, in drafting our introduction and discussion/conclusions we have also referenced articles analysing the theme of love and its classifications in terms of personal, social, and even health and well-being characteristics.

Given that our aim is to provide an initial review of scientific literature on the influence of different love styles on the quality and duration of the relationship between two people, the research was limited to articles of a high methodological quality. We have in any case considered complete projects published in peer-review journals, and have excluded summaries presented at seminars, reports introduced at conferences, dissertations, and comment articles that provided only partial data and authors’ opinions. We also excluded the articles we have not managed to retrieve, even upon direct request to the authors by e-mail.

The articles retrieved have been assessed by two independent reviewers. They were first selected based upon their title and abstract: 1943 articles to be potentially included in this review were identified on this basis. This initial screening also included papers dealing with love, love types, and love styles, even when not assessing the effects on the quality and duration of the love relationship. Upon a second selection based upon the titles and abstracts, we identified 235 articles concerning the general topic (love, love types, love styles) and retrieved their full text. We added a further 60 articles to these, and two reviewers have selected the abstract pool on the basis of the relevance of the topic dealt with to this review, and their methodological quality. This process has narrowed the pool to 122 articles. We successively focused only on those that concerned love styles in relation to quality and duration aspects in the love relationship, and for the purposes of the analysis we identified a sample of 22 articles (Figure 1).

Each of the 22 articles was analysed in depth, in an attempt to identify the theoretical basis, the goal and hypotheses, the research design, the procedure and tools utilized, as well as the main results recorded, using a specific, detailed method. In terms of systems and literature research, we have assessed the objectives, methods, and results obtained. As for the results, every publication has been summarized and classified in accordance with the six love styles described in Lee’s theory of love [1]. The method has been deemed by the researchers the most straightforward for a facilitated recognition of the effects of each love style on relational health and well-being. Throughout such phase, some doubts and perplexities about the inclusion of papers and their methodological quality were discussed between the two researchers, occasionally through the involvement of a third researcher.

In terms of methodological characteristics, we shall make a distinction between reviews and empirical research, in that we have adopted different method assessment criteria for each. For the reviews, we have identified the type, inclusion/exclusion criteria, the number of studies considered by the authors, and the reference population. As for the empirical research projects, we have assessed the method on the basis of the characteristics and origin of the sample, the type of sample, the setting, the procedure, the independent and dependent variables, and the tools used. We have identified two reviews, one by Acevedo and Aron [7] and one by Graham [9], both conducting a meta-analysis of the research projects assessed. Acevedo and Aron [7] conducted a meta-analysis of 25 researches and studies satisfying specific inclusion/exclusion criteria, including: duration of the relationship; focus on relational satisfaction (dependent variable) and love styles; romantic, obsessive, and companionate love; dimensions such as passion and intimacy (independent variables). Graham [9] selected 81 studies, which were required to: be in English; use a data collection method based on at least one of the measurements of love most utilized in literature (independent variables); and identify correlations between such metrics and relational variables, such as satisfaction and duration (dependent variables). Graham applied an inter-metric model of correlation that allowed to record common characteristics. Most of the 22 research papers apply a cross-sectional design and a quantitative approach. The research projects have been conducted in various different countries and cultures, and especially involved the white-Caucasian ethnic group or, in some cases, other ethnicities but as a minor percentage of the sample [20] [24] [25]. The only exception was the sample considered in the research by Smith and Klases [26], including 56 participants from the UK (London) and 52 from Hong Kong. Moreover, we found two studies focused on the Islamic population [27] [28] and others presenting a comparison between different cultures [25] [29].

The sample size ranged from 12 to 1582 participants. The latter were mostly single university students, though certain researches included married individuals [24] [30] or individuals in a committed love relationship [30] [31] [32]. The only two studies that considered (heterosexual) couples as well as the percentage of couples with children are that carried out by Gana et al. [23] and Vedes et al. [33]. Certain studies [34] [35] have considered clinical samples (patients suffering pathological love and jealousy), or partners that have experienced special situations such as cheating [36]. The samples included both females and males; only Honari and Saremi [37] have taken into consideration a female-only pool. The average age varied and the age range in most cases was quite broad. For example, in the research conducted by Lin & Huddleston-Casas [30] the range was 19 to 91 years. Where specified, participants mostly belonged to the middle class [20] [33].

Sampling was generally performed on a voluntary basis, though some authors used random sampling [24] [28]. Although most studies involved persons attending academic institutions such as universities, in certain cases participants were involved by means of advertisement, postings, e-mail, and other methods [24] [30] [33] [34].

Generally speaking, consent to take part in the research was requested to participants, while in certain studies it was also obtained from the institutions [29] [34].

Most of the research projects used standardized instruments, at times translated in the language spoken in the country where the research was conducted, then validated [29] and administered individually. In measuring love styles, a broadly used metric is the Love Attitudes Scale Short-Form (LAS-SF) [38]. Certain studies also adopt measurements designed ad hoc, especially for the assessment of relational dimensions [39], and a single study used the phone interview method [30]. The most important information about these aspects are synthetized in Table 2.

We have classified the results extrapolated from the researches in accordance with the six love styles identified by Lee [1]. This approach allowed us to organize content in relation to the correlations and influence that the different love styles may have on the health and well-being of a love relationship. At the same time, it allowed us to quote the reviewed articles more than once in case they dealt with more than one love style.

Eros love style and its relational correlates

This style expresses romantic love―distinguished by passion as well as physical and emotional attraction―is widely correlated to a high intensity of the love feeling, quality of life, and subjective well-being [40], as well as healthy love [34], and the various works analysed appear to confirm its positive value. In fact, it appears to be related to the good qualities of a relationship and of married life [28], as well as dyadic satisfaction [9] [20] [29] [33] [41]. The positive correlations are stable and do not change over time, in that they exist both in short and long-term relationships [7] [9] and in all age groups [41], nor do they mutate in different cultures, as recorded by Galinha et al. [29] who made a comparison between Americans, Mozambicans, and Europeans (Portugal). The positivity of the Eros love style is further attested by the results of researches that have proven its direct associations with specific dimensions, such as attachment security [29], the desire for intimate closeness to the partner [31], positive strategies for conflict resolution such as compromise [25], and dyadic coping, namely the joint effort by both partners to face a stressful situation lived by one of the two [33]. Besides, this love style is correlated to commitment in a relationship [20] expressed by a couple, which has expectations in terms of its duration, coherently with a romantic conception of love, as proved by the presence of negative emotions upon conclusion of the relationship [39]. Karandashev et al. [42] have recorded that in the initial phase of the relationship, Eros causes a decrease in avoidance, and anxiety diminishes, as part a dimension of the couple’s bonding process. As a further proof that the love style is positive, certain results highlight inverse proportionality between Eros and relational behaviour such as avoidance [32] or destructive communication behaviour―as identified by Gottman―including contempt, criticism, and defence [24], and with dysfunctional coping strategies such as interactional impulsiveness and dominance [25]. Moreover, Couch et al. [36] have recorded that Eros does not seem to correlate with the dysfunctional emotional reactions that couples often expressed in critical situations, such as emotional infidelity of the partner.

In a study by Galinha et al. [29], Eros appears to also have a mediation function between attachment and subjective well-being, at least in Mozambican and Portuguese participants―though not in American participants. This result suggests that a combination of secure attachment and Eros contributes in greater measure to subjective well-being in collectivist cultures―such as Mozambican and Portuguese cultures―as opposed to individualist cultures such as the American culture.

Despite the positive value Eros style in relationships is broadly confirmed, we have recorded a series of discrepant opinions. While Kimberly and Werner-Wilson [24] have observed a moderate correlation between Eros and dyadic coping, degree of affinity, and relational satisfaction, Adil and Kamal [27] recorded zero correlation with secure attachment and, instead, an existing correlation with the attachment style defined by Bartholomew and Horowitz [43] as “preoccupied” (preoccupied attachment style, distinguished by a negative perception of one’s self and others), though only in males. Goodboy and Myers [32] observed, instead, that Eros may exist in partners adopting negative relational behaviour, such as spying on the partner; the scholars argue that such behaviour may be adopted as a possible confirmation that the love relationship is experienced intensely and passionately. Ortalda and Clapetto [40] reported that Eros may even be correlated to feelings of jealousy. Smith and Klases [26] have observed that the length of a relationship is a significant predictor of the Eros style, but in a negative sense: the longer the relationships last, the less individuals show the love style. In the only reviewed research in which the scholars analyzed marital couples with the actor?partner interdependence model, some differences between husband and wife were observed. In fact, while a passionate attitude toward love of a couple’s partners influenced their own marital satisfaction (albeit to a lesser extent in the husbands) (actor effect), only the wife’s Eros style had a significant effect on her partner’s marital satisfaction (partner effect).

Agape love style and its relational correlates

Distinguished by altruistic attitudes and behaviour expressed by people that are most interested in providing support, care, and respect to the partner, this love style is positively correlated to relationship quality [28], length of the relationship [26], and relational satisfaction [30] [33] [41], regardless of the level of education, religiousness, or gender [30]. Moreover, this type of partner: always tends towards a more secure attachment [42] ; considers commitment an important characteristic in choosing a partner [39] ; tends towards avoiding destructive communication behaviour―such as that identified by Gottman, including contempt, criticism, and defence [24] ―and negative strategies for conflict resolution, such as dominance, but―on the other hand―uses positive modes such as compromise [25]. As recorded by Vedes et al. [33], a high level of Agape facilitates support to a stressed partner, and the joint effort to avoid stressors, although the latter coping type seems to be rarer in couples who have been together for longer. Furthermore, couples adopting such love type do not seem to show negative relational behaviour, such as jealousy or spying [32]. Couch et al. [36] have recorded that Agape couples tend to not show dysfunctional reactions after having been cheated on by a partner. Nonetheless, when a relationship ends Agape males in particular report that they feel negative emotions [39].

As for Eros, results that are partially contradictory with the majority of research―which emphasizes its positivity―have been recorded. For example, Agape is recorded to not be correlated to attachment security [27], but rather to an anxious dimension of attachment [26] and pathological love [34].

Moreover, in terms of the connection between Agape style and relational satisfaction, Fehr et al. [20] observed it does not exist, Vedes et al. [33] found a greater presence in women, and Kimberly and Werner-Wilson [24] found a greater presence in men. This last result has been confirmed also in the research of Gana et al. [23] who used the actor-partner interdependence model. In fact, they observed only the effect of a husband’s Agape style on his own marital satisfaction (actor effect). Neither significant result regarding the effect of a wife’s agape style on her own conjugal satisfaction (actor effect) nor the effect of each partner’s Agape style on the relational satisfaction of the other one has been found.

Ludus love style and its relational correlates

With its playful and uncommitted attitude towards love, and its inverse proportionality with the intensity of the love sentiment [40], this style is generally regarded as a risk factor for the quality and stability of the romantic relationship. Coherently with its theoretical definition, and in a couple’s relationship pathway, the Ludus style appears to affect all development, maintenance, and dissolution phases, in terms of weak effort in the relationship, lack of care for one’s commitment or that of one’s partner, and positive feelings upon termination of the relationship [20] [39].

In the relationship building phase Ludic people tend to desire a lack of closeness [31] and to mistrust one another from the very beginning, although they nonetheless show signs of desiring closeness, and show fluctuations in avoidance [42]. At the same time, though generally experiencing relational dissatisfaction [29] [33] [41], ludic people make attempts to keep the relationship alive, though they do so through negative behaviour such as destructive conflict, infidelity, avoidance, a and stimulation of jealousy in the other, as well as spying [32].

Ludus is considered a good predictor of behaviour triggering jealousy in the partner [32] [44] and destructive communicative behaviour such as that identified by Gottman as The Four Horsemen of the Apocalypse [24]. In conflict situations, Ludus couples tend to adopt―rather than constructive strategies such as compromise―destructive strategies, such as dominance and a greater impulsiveness in interactions [25]. Couch et al. [36] noted that when Ludus partners are cheated on, they do not manifest post-traumatic physical and psychological symptoms. Furthermore, Ludus is correlated to the avoidant form of attachment, as it is confirmed how partners with a playful attitude towards love tend to build adult insecure-avoidant attachment relationships [29].

Despite such clear and confirmed correlation between ludic behaviour and risk factors for the quality and duration of a relationship, certain research projects highlight gender differences and―as supported by Vedes et al. [33] ―hint how, still today, the love style is more socially accepted and considered more normal by and in men than in women. In fact, while in the view of Vedes et al. [33] relationship dissatisfaction is more frequent in ludic women rather than in men, Neto and Pinto [41] reported that adult men go as far as saying they are satisfied of their love life, whilst the love style appeared to be irrelevant in love satisfaction levels of young adults and older adults. Also in terms of a correlation with the preoccupied attachment form, Adil and Kamal [27] observed it is directly proportional in men and inversely proportional in women.

Storge love style and its relational correlates

There is a lack of research reporting significant data concerning this love style, based upon friendship and spending time with one another. It is considered a good predictor of married life quality [28] ; it is positively correlated with dyadic coping [24] and a progressive development of secure attachment [42] ; and in adults and older adults it is correlated with satisfaction in love life [41]. Moreover, it is associated to functional strategies to solve conjugal conflict―such as compromise―and is inversely related to dysfunctional strategies such as impulsiveness in interaction [25]. Couch et al. [36] reveal how there is no evidence that persons adopting this style, along with Eros, Pragma, and Agape, suffer negative consequences on the physical-psychological health following emotional infidelity by a partner.

While Galinha et al. [29] noted an absence of association between relational satisfaction and secure attachment, in the meta-analysis performed by Acevedo and Aron [7] it was recorded that the style is moderately correlated with relational satisfaction, mostly in long-term relationships rather than short-term relationships. It also appears to be a common style in long-term relationships, and when the relationships end, jealousy seems to be the main motivation [39]. On the other hand, Smith and Klases [26] observed how the longer the relationship, the more unlikely it is that partners show such friendly attitude in love.

Pragma love style and its relational correlates

Typical of people who express a pragmatic and rational attitude towards love, and for this reason tend to choose the partner based upon the characteristics they believe are important to them [39], Pragma appears to be linked to stable relationships [40], partially to the quality of married life [28], and to satisfaction in the relationship by adults and older adults [41]. It also contributes to the subjective well-being of people [29]. In conflict situations, pragmatic people generally utilize strategies such as compromise and avoidance [25], and when they suffer emotional infidelity by their partner, they do not have strong reactions [36]. Partners with this style do not appear to build an “anxious”, fearful attachment style―distinguished by a negative perception of one’s self and others, according to the typology identified by Bartholomew and Horowitz [27] ―but instead show uncertainty and fluctuations in the formation of an emotional attachment [42]. Galinha et al. [29] have not recorded any influence of this love style on secure attachment and on perception of the relational satisfaction of the partner.

Mania love style and its relational correlates

Mania is the expression of a manic attitude towards love, implying possessive and obsessive behaviours: it is considered the purest form of romantic obsession [7] [9]. It is perhaps due to such characteristic that it is considered and consolidated as an important risk factor in quality of married life. Despite it involves people that tend to commit to the relationship [20], such people do not appear to be able to build long-term relationships [26] or satisfying relationships [7], with a few exceptions. In fact, Neto & Pinto [41] recorded a correlation between love life satisfaction in manic male adults, but not females. Mania is a strong predictor of negative relational behaviour. It is correlated to jealousy [40] and exists in people expressing pathological jealousy [35] and pathological love [34] [35], and that tend to manifest jealousy-evoking behaviour in the partner, even when they are shown affection by the latter [44]. Partners adopting a manic love style tend to express an excessive need to be reassured by the partner [44], emotional highs and lows in the ability to be close to him/her [42], an anxious-ambivalent attachment style [37], and preoccupation for the relation and its termination [39]. On the other hand, Smith and Klases [26] recorded an inverse proportionality with the anxious component of attachment. Manic people tend to exercise negative relational behaviour to keep the relationship alive, such as destructive conflict, infidelity, allowing control and spying [32]. In their cultural analysis, Galinha et al. [29] revealed how Mania is inversely proportional to secure attachment in their Mozambican sample, but not in the American or Portuguese participants.

It is directly proportional to destructive communication behaviour such as that identified by Gottman [24], and is the main predictor of negative reactions following infidelity by a partner, in that people adopting this style tend to: live infidelity in a traumatic manner, express unresolved feelings related to the event experienced, and suffer physical symptoms, acute stress, unease, anxiety, depression, and struggle to forgive [36].