Relationship satisfaction and sexual satisfaction: a longitudinal study of individuals in long-term relationships.

Both therapists and the general public see the quality of a couple's romantic relationship and the quality of their sex life as linked (Sprecher, 1998; Wincze & Carey, 2001). In fact, researchers consistently have shown that there is a strong positive association between relationship satisfaction and sexual satisfaction (e.g., Haavio-Mannila & Kontula, 1997; Purnine & Carey, 1997). Authors often make implicit assumptions about the direction of this relationship to inform theory and practice. However, there has been little research investigating whether there is a causal relationship between the two variables and, if so, its direction.

The Interpersonal Exchange Model of Sexual Satisfaction proposes that relationship quality affects sexual satisfaction (Lawrance & Byers, 1995). In keeping with this view, partners' experiences of unresolved conflicts, not feeling loved, and emotional distance have been shown to be associated with lower sexual satisfaction (Davidson & Darling, 1988; Schenk, Pfrang, & Rausche, 1983). In addition, MacNeil and Byers (2005) found that relationship satisfaction partially mediates the association between self-disclosure and sexual satisfaction. The authors interpreted this finding as indicating that self-disclosure leads to greater relationship satisfaction, which in turn leads to higher sexual satisfaction. Further, O'Leary and Arias (1983) found that marital therapy that focused on nonsexual relationship issues resulted in significant increases in sexual satisfaction.

Alternately, it may be that the level of sexual satisfaction impacts the affective evaluation of the overall relationship (i.e., relationship satisfaction). For example, relationship enhancement programs include improvement of the sexual relationship as a way to promote future relationship adjustment (Floyd, Markman, Kelly, Blumberg, & Stanley, 1995). This view also is inherent in measures of relationship adjustment, such as the widely used Dyadic Adjustment Scale (Spanier, 1976). That is, these measures typically include items assessing the sexual relationship in calculating a total relationship adjustment/satisfaction score. In the current study, unidimensional, global measures were used to assess both sexual satisfaction and relationship satisfaction.

It may also be that the association between sexual satisfaction and relationship satisfaction is bidirectional. Data from a 2-year longitudinal study of newly married couples supports this view (Henderson-King & Veroff, 1994). However, Henderson-King and Veroff used cross-lag correlations to assess directionality. Cross-lag correlations do not provide sound information about cause and effect because they fail to control for the association of the two variables at Time 1 (Fincham, Beach, Harold, & Osborne, 1997; Rogosa, 1980). In a longitudinal study of dating couples, Sprecher (2002) assessed the association between relationship satisfaction and sexual satisfaction using the appropriate statistical controls. She found evidence that change in relationship satisfaction is associated with change in sexual satisfaction. However, consistent with the Henderson-King and Veroff study, she did not find evidence to support either causal direction. This may be because Sprecher used a 2-item measure of sexual satisfaction with unknown reliability and validity. Alternately, it may be because her sample consisted of individuals in the early stages of their relationships. Relationship satisfaction is more strongly associated with sexual satisfaction early in relationships than it is in long-term relationships (Byers, 1999), a phenomenon that may have obscured the longitudinal association between these two variables.

Finally, it may be that the association between sexual satisfaction and relationship satisfaction reflects the influence of a third variable. There is indirect evidence to suggest that the quality of intimate communication might account for concurrent changes in relationship satisfaction and sexual satisfaction--that is, that poor communication results in both decreased relationship satisfaction and deceased sexual satisfaction. Communication has been shown to be associated with both relationship satisfaction and sexual satisfaction (Byers & Demmons, 1999; Cupach & Comstock, 1990; Fowers & Olson, 1989). In addition, Markman (1979, 1981) found that for couples planning marriage, although unrewarding communication patterns were not associated with concurrent relationship adjustment, these patterns were predictive of marital distress 5 years later. If communication does account for concurrent changes in sexual and relationship satisfaction, the association between changes in the two variables would be reduced when communication is controlled.

It may be that the causal association between relationship satisfaction and sexual satisfaction differs for women and men. The traditional sexual script prescribes greater interest in sexual activity for men than for women. For women, satisfying sex is expected to occur only within the context of a loving relationship. In contrast, men are expected to be highly motivated to engage in sexual activity both inside and outside of long-term relationships. Vohs, Catanese, and Baumeister (2004) concluded that, consistent with the traditional sexual script, research has consistently shown that men have a stronger sexual motivation than do women. Further, Sprecher (2002) found that relationship satisfaction (but not sexual satisfaction) negatively predicted the likelihood of relationship breakup for women but not for men. In contrast, sexual satisfaction (but not relationship satisfaction) negatively predicted the likelihood of relationship dissolution for men but not for women. Thus, it may be that for men decreased sexual satisfaction leads to decreased relationship satisfaction, whereas for women, the reverse is true.

The goal of this study was to explore the association between relationship satisfaction and sexual satisfaction over time in men and women in long-term relationships in order to provide evidence about possible causal explanations for the association between the two variables. Showing that one variable predicts change in the other variable over time is necessary for establishing causality (Rosenthal & Rosnow, 1991; Ruvolo, 1998). For example, a finding that relationship satisfaction predicts change in sexual satisfaction would be consistent with the hypothesis that relationship quality affects sexual satisfaction. A finding that relationship satisfaction does not predict change in sexual satisfaction would be inconsistent with the hypothesized causal relationship. The hypothesis that communication accounts for concurrent changes in sexual and relationship satisfaction was also explored.

METHOD

Participants and Procedure

Community members as well as staff, alumni, and students at a medium-sized co-ed university were recruited for a study of long-term sexual relationships. At Time 1, we mailed questionnaires to randomly selected university alumni regardless of location (n = 790), all university staff (n = 763), and members of the community who responded to posters and newspaper advertisements (n = 103). We sent only one questionnaire to any address to ensure that none of the participants were in relationships with each other. Questionnaire packages included a cover letter detailing the nature of the study and requesting participation by individuals in relationships of one year or longer, as well as a questionnaire with its own preaddressed, stamped return envelope.

At Time 1, 94 men and 150 women in opposite-sex relationships (1 individual in a same-sex relationship was dropped from the study to increase the homogeneity of the sample) returned completed questionaires. No attempt was made to preselect individuals in long-term relationships, and thus the return rate from individuals who were eligible to participate could not be determined. However, the minimum return rate (assuming all individuals who received a questionnaire were in a long-term relationship) was 13% for alumni, 6% for university staff, and 41% for community members.

Participants who were willing to complete a follow-up questionnaire provided their name and address on a postcard that was returned separately. We mailed follow-up questionnaires to these participants 18 months after the initial mailing (Time 2). (Data from a 3-month follow-up were not used in the current study as 18 months provided a better test of the longitudinal hypotheses.) We made no attempt to find participants who had moved. Eighty-seven Time 1 participants (34 men and 53 women; 36%) completed the Time 2 questionnaire and indicated that they were with the same partner as at Time 1. To match the Time 1 and Time 2 questionnaires while maintaining anonymity, participants devised their own code number according to instructions provided on both questionnaires. Lawrance and Byers (1995) reported Time 1 data.

I conducted two separate MANOVAs to determine whether respondents who completed the questionnaire at Time 1 and Time 2 differed from those who only completed the Time 1 questionnaire. The two groups did not differ in their demographic characteristics (gender, age, length of relationship, relationship status, having a child living at home), F(5, 236) = 0.84, p = .521. They also did not differ in their Time I relationship satisfaction or sexual satisfaction scores, F(2, 236) = 0.62, p = .540. The 87 participants who completed both questionnaires ranged in age from 23 to 61 (M = 37.7, SD = 10.0). At Time 1, respondents had been with their present partner for between 1 and 35 years (M = 12.2, SD = 9.3); most were married (85%) and had children living at home (82%). Although ethnicity was not assessed, in keeping with the ethnic composition of both the province and the university, it is highly likely that the sample was primarily Caucasian. Nine participants (10%) reported that they and/or their partners had been in therapy during the 18 month follow-up period. Although 3 of these individuals reported being in therapy for relationship issues, they were retained in the sample because, at Time 1, they reported being relationally satisfied.

Measures

Participants completed the Interpersonal Exchange Model of Sexual Satisfaction (IEMSS) Questionnaire (Lawrance & Byers, 1998) at Time 1 and Time 2, as well as some additional items that differed at each administration. Only the measures that are related to the goals of this study are described here.

Background questionnaire. A background questionnaire was used to collect demographic information such as gender, age, type and length of current relationship, and number of children living in the home.

Global Measure of Relationship Satisfaction (GMREL; Lawrance & Byers, 1998). The GMREL assessed satisfaction with the overall relationship. Respondents rated their relationship with their partner on five 7-point bipolar scales: good-bad, pleasant-unpleasant, positive-negative, satisfying-unsatisfying, valuable-worthless. Possible scores on the GMREL range from 5 to 35, with higher scores indicating greater relationship satisfaction. Lawrance and Byers (1998) provided evidence for the reliability and validity of the GMREL. Internal consistency of the GMREL was high for the present sample ([alpha] = .95 at Time 1 and .96 at Time 2).

Global Measure of Sexual Satisfaction (GMSEX; Lawrance & Byers, 1998). The GMSEX is identical to the GMREL except participants rate their sexual relationship with their partners. Lawrance and Byers provided evidence for the reliability and validity of the GMSEX. Internal consistency was high for the present sample ([alpha] = .96 at both time periods).

Primary Communication Inventory (PCI; Navran, 1967). The PCI is a 25-item measure that was used to assess the quality of verbal and nonverbal communication within the respondent's relationship at Time 2 only. Items are rated on a 5-point scale ranging from never to very frequently. Navran (1967) found the PCI to have good validity. Internal consistency in the present study was good ([alpha] = .81).

RESULTS

I used hierarchical multiple regression analyses to investigate the association between relationship satisfaction and sexual satisfaction over time. To control for extraneous variance, I assessed the correlation between relationship satisfaction at Time 1 and sexual satisfaction at Time 2 after controlling for sexual satisfaction at Time 1, and vice versa. As a result, the criterion being analyzed for other predictors were residuals (or changes) in satisfaction from Time 1 to Time 2. Thus, if relationship satisfaction influences sexual satisfaction, relationship satisfaction at Time 1 would predict the change in sexual satisfaction from Time 1 to Time 2. In contrast, if sexual satisfaction influences relationship satisfaction, sexual satisfaction at Time 1 would predict the change in relationship satisfaction from Time 1 to Time 2.

In the first analysis, sexual satisfaction at Time 2 served as the dependent variable (see Table 1). I entered sexual satisfaction at Time 1 on the first step to control the overlap between sexual satisfaction at the two time periods. As a result, the criterion being analyzed for the other predictors were changes in sexual satisfaction from Time 1 to Time 2. The addition of relationship satisfaction at Time 1 on the second step did not add significantly to the multiple R, indicating that relationship satisfaction at Time 1 was not associated with the change in sexual satisfaction between Time 1 and Time 2. Finally, I entered relationship satisfaction at Time 2 on the third step, which added significantly to the prediction of sexual satisfaction at Time 2. This indicates that changes in sexual satisfaction between Time 1 and Time 2 were accompanied by similar changes in relationship satisfaction over the same period.

I tested gender differences in the association between relationship satisfaction at Time 1 and sexual satisfaction at Time 2 using partialled products based on centered variables (Cohen, Cohen, & West, 2003). After controlling for sexual satisfaction and relationship satisfaction at Time 1, neither gender nor the interaction between gender and relationship satisfaction at Time 1 added significantly to the prediction of sexual satisfaction at Time 2. This indicates that relationship satisfaction was not associated with the change in sexual satisfaction between Time 1 and Time 2 for either the men or the women.

In the second analysis, relationship satisfaction at Time 2 served as the dependent variable (see Table 2). After I controlled for relationship satisfaction at Time 1, entry of sexual satisfaction at Time 1 on the second step did not add significantly to the multiple R. This indicates that sexual satisfaction at Time 1 was not related to the change in relationship satisfaction between Time 1 and Time 2. I entered sexual satisfaction at Time 2 on the third step, and it added significantly to the prediction of relationship satisfaction at Time 2. This indicates that the changes in relationship satisfaction between Time 1 and Time 2 did predict the changes in sexual satisfaction between Time 1 and Time 2. After I controlled for relationship satisfaction and sexual satisfaction at Time 1, neither gender nor the interaction between gender and sexual satisfaction at Time 1 added significantly to the prediction of relationship satisfaction at Time 2. This indicates that sexual satisfaction at Time 1 was not associated with change in relationship satisfaction between Time 1 and Time 2 for either the men or the women.

Together, these analyses indicate that relationship satisfaction and sexual satisfaction changed concurrently from Time 1 to Time 2. However, there was no evidence that relationship satisfaction or sexual satisfaction at Time 1 was causally linked to the other form of satisfaction at Time 2 for either men or women.

Communication Quality and Changes in Satisfaction

Next I examined whether a third variable, the quality of intimate communication, accounted for the concurrent changes in sexual and relationship satisfaction using the procedures recommended by Baron and Kenny (1986). Participants with better communication reported higher relationship satisfaction (r = .61 at Time 1 and r = .69 at Time 2, p = .000) and higher sexual satisfaction (r = .40 at Time 1 and r = .52 at Time 2, p = .000). The results of these analyses are presented as Model 2 in Tables 1 and 2.

Communication added significantly to the prediction of sexual satisfaction at Time 2 after controlling for sexual satisfaction and relationship satisfaction at Time 1, indicating that communication was associated with the change in sexual satisfaction (see Table 1). The addition of relationship satisfaction at Time 2 also significantly increased the prediction of sexual satisfaction at Time 2. However, the [beta] for relationship satisfaction at Time 2 was reduced from [beta] = .49 to [beta] = .43.

A parallel analysis predicting relationship satisfaction at Time 2 yielded similar results (see Table 2). After I controlled for relationship satisfaction and sexual satisfaction at Time 1, communication significantly added to the prediction of relationship satisfaction at Time 2, indicating that communication was associated with the change in relationship satisfaction. The addition of sexual satisfaction at Time 2 also significantly increased the prediction of relationship satisfaction at Time 2. Again, the [beta] was reduced from [beta] = .64 to [beta] = .50. These results indicate that the quality of communication was associated with change in both relationship satisfaction and sexual satisfaction. Further, communication partially accounted for concurrent changes in relationship satisfaction and sexual satisfaction.

Exploratory Analyses

It may be that the causal relationship between relationship satisfaction and sexual satisfaction differs for individuals whose satisfaction is increasing compared to those whose satisfaction is decreasing. This would have obscured the results in the previous analyses. Therefore, I used separate exploratory multiple regression analyses to test the association between relationship satisfaction and change in sexual satisfaction from Time 1 to Time 2 for (a) the 28 individuals whose sexual satisfaction had increased, and (b) the 35 individuals whose sexual satisfaction had decreased. (The sexual satisfaction of 21 individuals had not changed.) As was the case for the complete sample, relationship satisfaction did not predict change in sexual satisfaction from Time 1 to Time 2 for individuals whose sexual satisfaction had decreased. However, for those individuals whose sexual satisfaction had increased, after I controlled for sexual satisfaction at Time 1 ([R.sup.2] = .78), relationship satisfaction at Time 1 added to the prediction of sexual satisfaction at Time 2 ([R.sup.2] change = .05, F[1, 24] = 4.29, p = .049). These results indicate that for this group, individuals with higher relationship satisfaction at Time 1 reported a greater increase in their sexual satisfaction from Time 1 to Time 2.

Likewise, I used separate regression analyses to test whether sexual satisfaction predicted the change in relationship satisfaction from Time 1 to Time 2 for (a) the 27 individuals whose relationship satisfaction had increased, and (b) the 31 individuals whose relationship satisfaction had decreased from Time 1 to Time 2. (The relationship satisfaction of 28 individuals had not changed.) As was the case for the complete sample, sexual satisfaction did not predict change in relationship satisfaction for those individuals whose relationship satisfaction had increased. However, for those individuals whose relationship satisfaction had decreased, after I controlled for relationship satisfaction at Time 1 ([R.sup.2] = .51), sexual satisfaction at Time 1 added uniquely to the prediction of sexual satisfaction at Time 2 ([R.sup.2] change =. 13, F[1, 28] = 9.82, p = .004). These results indicate that for this group, individuals with lower sexual satisfaction at Time 1 reported a greater decrease in their relationship satisfaction from Time 1 to Time 2.

DISCUSSION

This study examined the association between sexual satisfaction and relationship satisfaction over an 18-month period. As one of only a handful of longitudinal studies in the area, the results add to our understanding of the association between relationship satisfaction and sexual satisfaction over time. Before discussing the results, a number of limitations should be noted. The response rate was low at Time 1, and only 36% of the Time 1 sample completed the questionnaire 18 months later, raising the possibility that the results were affected by selection bias. However, individuals who participated at both time periods did not differ from the rest of the Time 1 sample in their demographic characteristics, relationship satisfaction, or sexual satisfaction. In addition, the sample was fairly small and homogeneous, consisting for the most part of highly educated Caucasian individuals who reported being relationally and sexually satisfied.

Consistent with past research, individuals with greater relationship satisfaction also reported greater sexual satisfaction (Haavio-Mannila & Kontula, 1997; Purnine & Carey, 1997). In addition, changes in sexual satisfaction were associated with changes in relationship satisfaction for these individuals in long-term relationships, as Sprecher (2002) found in her study of dating couples. However, there was only limited evidence based on exploratory analyses to support a causal connection in either direction. That is, in the complete sample there was no evidence to support either the view that low sexual satisfaction leads to a decrease in relationship satisfaction or the view that low relationship satisfaction leads to a decrease in sexual satisfaction for either men or women. Thus, it may be that very small increments or decrements in relationship satisfaction cause equally small changes in relationship satisfaction (or vice versa) over so short a time period that relationship satisfaction and sexual satisfaction change concurrently. Of course, given the correlational nature of this study, these results cannot be used to disprove either causal hypothesis. Thus, for example, it also may be that there is a causal relationship between relationship satisfaction and sexual satisfaction, but it occurs over a longer time frame than the 18 months examined in this study.

The findings from the exploratory analyses suggest one possible explanation for why the current study and past research have failed to find evidence for a causal relationship between relationship satisfaction and sexual satisfaction. That is, there may not be a single causal direction between relationship satisfaction and sexual satisfaction. Rather, it may be that in some situations or for some individuals, low sexual satisfaction causes a decrease in relationship satisfaction. In the current study, low sexual satisfaction at Time 1 was associated with a greater decrease in relationship satisfaction only for individuals whose relationship satisfaction was decreasing. For these individuals it may be that low sexual satisfaction represented one more problem area that added to the overall decline in relationship satisfaction. In other situations or for other individuals, the causal direction might be reversed. In this study, higher relationship satisfaction was associated with a greater increase in sexual satisfaction only for individuals whose sexual satisfaction was increasing.

Past research has shown that intimate communication is associated with both sexual satisfaction and relationship satisfaction (Cupach & Comstock, 1990; Fowers & Olson, 1989). Our results extend past research by demonstrating that communication is also associated with changes in both relationship satisfaction and sexual satisfaction over time. That is, poor communicators were likely to report decreases in both relationship satisfaction and sexual satisfaction over the 18 months of the study, whereas good communicators were likely to report increases in satisfaction. Further, communication quality accounted for some of the concurrent changes in the two variables. This suggests that poor communication results in decreased satisfaction in a number of areas of relationship functioning, including sexual satisfaction and overall relationship satisfaction.

In sum, the results suggest that past research and therapeutic interventions based on implicit or explicit assumptions about the nature of the longitudinal association between relationship satisfaction and sexual satisfaction have been too simplistic. Researchers need to develop and validate more complex models than they have used in the past that incorporate situational variables as well as individual and relationship characteristics. That is, we need to ask for which individuals and in what situations low relationship satisfaction leads to decreased sexual satisfaction, and for whom and in what situations the reverse occurs. The results of this study suggest that communication quality is one such variable, although not the only factor since communication accounted for only part of the concurrent changes in relationship satisfaction and sexual satisfaction. The results do not, however, support propositions based on the traditional sexual script that the direction of the association between relationship satisfaction and sexual satisfaction differs for men and women. Only by developing more sophisticated models are we likely to gain insight into the complex interplay of relationship satisfaction and sexual satisfaction.

Table 1. Hierarchical Multiple Regression Analysis Predicting
Sexual Satisfaction at Time 2

                                  Model 1 (a)

Predictor         r     [beta]    sr     [R.sup.2] change   F change

GMSEX T1        .74 *    .74     .74 *         .55          103.48 *
GMREL T1        .50 *    .07     .06           .00            0.60
Communication   .52 *     --      --            --             --
GMREL T2        .65 *    .49     .38           .14           38.27 *

                               Model 2 (b)

Predictor       [beta]    sr     [R.sup.2] change   F change

GMSEX T1         .74     .74 *         .55          103.48 *
GMREL T1         .07     .06           .00            0.60
Communication    .32     .26 *         .07 *         14.42 *
GMREL T2         .43     .29 *         .08 *         22.42 *

Note. N = 87; F(3, 83) = 62.60, p = .000; GMSEX T1 = sexual
satisfaction at Time 1; GMREL T1 = relationship satisfaction at
Time 1; GMREL T2 = relationship satisfaction at Time 2.

(a) [R.sup.2] = .69, F(3, 83) = 62.60, p = .000.

(b) [R.sup.2] = .70, F(4, 82) = 38.13, p = .000.

* p < .001.

Table 2. Hierarchical Multiple Regression Analysis Predicting
Relationship Satisfaction at Time 2

                                   Model 1 (a)

Predictor         r     [beta]    sr     [R.sup.2] change   F change

GMREL T1        .64 *    .64     .64 *         .41          58.22 *
GMSEX T1        .45 *    .09     .07           .01           0.76
Communication   .69 *     --      --            --           --
GPASEX T2       .65 *    .64     .43           .19          38.27 *

                                  Model 2 (b)

Predictor       [beta]    sr     [R.sup.2] change   F change

GMREL T1         .64     .64 *         .41          58.22 *
GMSEX T1         .09     .07           .01           0.76
Communication    .48     .38 *         .14          26.64 *
GPASEX T2        .50     .31 *         .10          22.42 *

Note. N = 87; F(3, 83) = 41.06, p = .000; GMSEX T1 = sexual
satisfaction at Time 1; GMSEX T2 = relationship satisfaction at
Time 2; GMREL T1 = relationship satisfaction at Time 1.

(a) [R.sup.2] = .60, F(3, 83) = 41.06, p = .000.

(b) [R.sup.2] = .65, F(4, 82) = 38.13, p = .000.

* p < .001.

I would like to thank Sheila MacNeil for her assistance with data preparation and Barry Spinner for his suggestions regarding data analysis. Shannon Archibald, Jacqueline Cohen, Andrea Miller, Heather Sears, and Angela Weaver provided valuable feedback on an earlier draft of this manuscript. Data at Time 1 were collected by Kelli-an Lawrance, now at Brock University in St. Catharines, Ontario, for her doctoral dissertation.

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Manuscript accepted August 11, 2004

E. Sandra Byers

University of New Brunswick

Address correspondence to E. Sandra Byers, Ph.D., Department of Psychology, University of New Brunswick, Fredericton, N.B. E3B 6EA, Canada; e-mail: [e-mail].