Running head: TYPE D PERSONALITY AND PERCEIVED STRESS 1. Type D Personality and Perceived Stress: The Mediating Effect of Social Support

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1 Running head: TYPE D PERSONALITY AND PERCEIVED STRESS 1 Type D Personality and Perceived Stress: The Mediating Effect of Social Support Yanne Eijkenboom Tilburg University Author Note Yanne Eijkenboom SNR: u , ANR: Under supervision of Stefanie Duijndam, MSc Bachelor thesis, Psychology and Health Department Medical and Clinical Psychology, Tilburg University February, 2017

2 TYPE D PERSONALITY AND PERCEIVED STRESS 2 Abstract Type D personalities, who possess a combination of the personality traits social inhibition and negative affectivity, might experience more perceived stress. Perceived stress could generate a higher risk for coronary heart diseases and other health issues. The buffering hypothesis predicted that more social support could lessen perceived stress. The current study aimed to examine the relationship between Type D personality and perceived stress and the mediating effect of social support. The study was conducted at Tilburg University, with 209 undergraduate students (160 women, 41 men; M age = 20.3 years, SD age = 2.08), selected through convenience sampling, with a between-subjects design. Participants were divided into four personality groups: Type D, negative affectivity, social inhibition, and a reference group. The study used a demographics questionnaire and the Type D Personality Scale (DS-14), the Perceived Stress Scale (PSS), and the Multidimensional Scale of Perceived Social Support (MSPSS). The analyses showed no significant differences in demographics. ANOVA analyses showed an effect of negative affectivity on stress and an effect of social inhibition on social support. An ANCOVA analysis showed a small mediating effect of social support on the relationship between personality type and perceived stress. This effect supports the buffering hypothesis, but it was not persuasive enough to alleviate the effect of personality type on stress. Further research is recommended into the separate and the interaction effect(s) of social inhibition and negative affectivity and into what can alleviate stress in different populations. Keywords: Type D, social inhibition, negative affectivity, social support, perceived stress

3 TYPE D PERSONALITY AND PERCEIVED STRESS 3 Type D Personality and Perceived Stress: The Mediating Effect of Social Support While coronary heart diseases (CHD) are the number one cause of death in the western society, research shows that a lot of cases of CHD cannot be explained by standard risk factors, such as smoking, hypertension, and lack of exercise (U.S. Department of Health and Human Services, 2016; Denollet, 2005). Some of these cases can be explained by psychosocial and personality factors, such as anger, hostility, and negative affects (e.g. anxiety and depression), which can lead to a higher risk for CHD (Booth-Kewley & Friedman, 1987; Denollet, 1997). Also emotional distress a negative and stable state over time in which life events are perceived to be stressful can result in higher prevalence, progression, and mortality of CHD (Denollet, 1997; Denollet, Pedersen, Vrints, & Conraads, 2013, Williams & Wingate, 2012). Twenty years ago, Denollet (1997) identified a new personality type, Type D, that consists of a combination of two personality traits: social inhibition and negative affectivity. The interaction of these traits within Type D personalities lead to higher perceived emotional distress and therefore a higher risk of developing CHD (Denollet, 1997; Denollet et al., 1996). The personality trait social inhibition is the inhibition of self-expression (i.e., emotions and behavior) in social interactions (Asendorpf, 1993; Denollet, 2013). Those scoring high on social inhibition continuously anticipate unsatisfactory reactions from the outside world, such as disapproval and low regard, making them actively push away available social support as self-protection (Denollet, 1997, 2005). The personality trait negative affectivity is the tendency to experience negative emotions (e.g., stress, anxiety, and depression) and discomfort across time and situations, even in the absence of overtly stressful situations (Watson & Clark, 1984). Those scoring high on negative affectivity are relatively more

4 TYPE D PERSONALITY AND PERCEIVED STRESS 4 introspective and tend to dwell on the negative side of themselves and the world (Watson & Clark, 1984). Later research shows that the Type D personality is not only a predictor of perceived stress for CHD-patients, but also negatively correlated with health for non-cardiovascular populations (Mols & Denollet, 2010; Williams & Wingate, 2012). The higher levels of perceived stress can lead to both somatic and psychological health issues e.g. vulnerability to illness, poor self-management, and mood disturbances (DeLongis, Folkman, & Lazarus, 1988). In addition, Type D personalities also have a lower and poorer quality of social support (Denollet, 2000; Williams et al., 2008). Social support consists of interpersonal relations (i.e. a significant other, friends, and family), that provide informational, instrumental, or emotional assistance, such as love and care (Cohen & McKay, 1984). Perceived social support is the amount of support one perceives to have in threatening and stressful situations (Diong et al., 2005). Perceived social support is relatively stable over the years and barely correlated with the actual received social support. However, perceived social support appears to be a better predictor of health and wellbeing than received support (Ditzen & Heinrichs, 2014). Research by Chao (2011, 2012) shows that low levels of support can create a higher vulnerability to stress, resulting in lower well-being. High perceived social support is beneficial for physical health, quality of life, well-being, and it may lessen perceived stress (Ben-Zur, 2009; Diong et al., 2005; Panayiotou & Karekla, 2012). The theory of this protective effect of social support on stress is called the buffering hypothesis, which states that social support can lower stress and therefore stressrelated health issues (Cohen & Wills, 1985; Schwarzer & Leppin, 1989). In the study of Cohen and McKay (1984), they state that the buffering effect of certain social support might only be effective for relevant stressful conditions and experiences.

5 TYPE D PERSONALITY AND PERCEIVED STRESS 5 Although there has been a lot of research on both Type D and the buffering hypothesis, there has not been much research on whether the buffering hypothesis also has an effect for Type D personalities. Previous research on the mediating effect of social support on the relationship between Type D and psychological distress has been done by Polman, Borkoles, and Nicholls (2010). Their analyses show that social support, either from family or friends, does not have any significant mediating effect between Type D and psychological distress. However, research by Williams and Wingate (2012) on the relationships between Type D, social support, and perceived stress, shows that social support does partially mediate Type D and perceived stress both the total and the direct effect were significant. These inconsistent findings are reason for further research to see whether the buffering effect of social support can lessen perceived stress for Type D personalities. The Type D approach is bimodal instead of a spectrum and subjects are categorized as either high or low on social inhibition and negative affectivity instead of on a continuum (De Fruyt & Denollet, 2002; Denollet, 2005; Mols & Denollet, 2010). Many recent studies have reduced the four groups of the 2-by-2 taxonomy (high/low negative affectivity and high/low social inhibition) to only Type D and non-type D personalities (see Figure 1, for a visual display of the taxonomy). Little research has been done on the separate effects of social inhibition and negative affectivity and whether the combination is vital (Denollet et al., 2013; Grande, 2010). Nevertheless, Denollet (1997) did test a 2-by-2 design for the interaction of negative affectivity and social inhibition, whose analyses show that only the Type D personality has a significant effect on CHD prognosis, in contrast to the other three personality groups. By integrating theories about Type D, social support, and the buffering hypothesis the current study aims to investigate the relationship between Type D personality and perceived stress and whether the amount of stress depends on social support. Because previous research

6 TYPE D PERSONALITY AND PERCEIVED STRESS 6 mostly compared Type D personality with non-type D personality, the current study will make a comparison between all four personality types (see Figure 1) to see whether these are distinguishable in their effects. Based on the findings of Denollet (1997), the first hypothesis of the current study is that the Type D personalities will have more perceived stress than the other three personality types. Based on the buffering hypothesis, the second hypothesis is that the differences between the personality types in perceived stress will diminish when controlled for social support. Method Procedure and Participants The current study was conducted in the context of larger study done at the Medical and Clinical Psychology department of Tilburg University. This study, called the INHIBIT study, researched the psychobiology of interpersonal interaction as an approach for uncovering individual differences. The participants, 209 undergraduate psychology students at Tilburg University, were recruited through convenience sampling and were rewarded for their participation with participation credits. The psychology department of the university had obtained ethical approval from the ethics committee prior to testing and participants provided informed consent prior to participating. Participants needed to fill in questions for demographics (age, gender, etc.) and were asked to complete a whole questionnaire pack about a variety of subjects (total survey time approximately 40 min.). In the current study, only the demographics and three questionnaires (i.e. DS-14; PSS-10; MSPSS) were used in the analyses. Relevant articles and information were searched by use of the web-database PsychInfo. The search terms that were used and combined were: social support, support system, (perceived) stress, (psychological/emotional) distress, Type D (personality), social inhibition, negative affectivity, buffering hypothesis, and other relevant thesaurus synonyms.

7 TYPE D PERSONALITY AND PERCEIVED STRESS 7 To narrow the amount of search hits extra demands were used (e.g. timeframe after 2000, published in academic journals only, full text available). Questionnaires Type D Personality Scale. The DS-14 questionnaire (Denollet, 2005) tested both personality traits i.e. social inhibition and negative affectivity and Type D personality. The traits were each assessed by 7 statements in the questionnaire (negative affectivity; e.g., I take a gloomy view of things and social inhibition; e.g. I would rather keep other people at a distance) which were rated on a 5-point Likert-scales (0 = false and 4 = true). The scoring of the two personality traits, social inhibition and negative affectivity, was sub-scaled on a range between 0 to 28 points. The Type D personality score is based on a predetermined (standardized cut-off point) median-split (score above 10 for both social inhibition and negative affectivity). For the other three personality groups the same assessment was used, meaning that a score above 10 for negative affectivity, but not for social inhibition, would place you in a group with only the trait negative affectivity, and vice versa. Those who scored below 10 on both subscales were placed in the reference group. The validity of the assessment in the current study had a Cronbach s alpha of.87. Perceived Stress Scale. The 10-item Perceived Stress Scale (PSS; Cohen, Karmarck, & Mermelstein, 1983) was used to assess the perceived stress over life-events from the past month of the respondents (e.g., In the last month, how often have you been upset because of something that happened unexpectedly?). Answers were rated on a five-point Likert-scale anchored 0 (never) to 4 (very often). The scoring has been based upon the total sum score of the items, ranging from 0 to 40, with higher scores indicating more perceived stress. The scale showed in the current study a Cronbach s alpha of.84. Multidimensional Scale of Perceived Social Support. To assess the levels of perceived social support the Multidimensional Scale of Perceived Social Support (MSPSS;

8 TYPE D PERSONALITY AND PERCEIVED STRESS 8 Zimet, Dahlem, & Zimet, 1988) was used. The questionnaire contained 12 items to assess social support from family (e.g. I can talk about my problems with my family), from friends (e.g. I have friends with whom I can share my joys and sorrows), from significant others (e.g. I have a special person who is a real source of comfort to me) and total social support. The scoring for each item had a maximum of 7, making the range of the total sum score of the items between 0 and 84 points, with a higher score indicating more perceived social support. The scale had a high level of internal consistency in the current study with a Cronbach's alpha of.90. Statistical Analyses After the assumptions were checked, the reliability of the scales and the frequencies of the demographics were determined with SPSS. Subsequently two ANOVA analyses were conducted to assess the effect of the four personality types on both perceived stress and social support. Thereafter, an ANCOVA analysis was conducted to test the mediating effect of social support on the relationship between Type D and perceived stress in a between-subjects design. Personality type was entered as the independent factor, perceived stress as the dependent factor, and social support was entered as the covariate. Results Demographic Variables All 209 undergraduate students who participated in the study have been analyzed (160 women, 49 men, M age = 20.3 years, SD age = 2.08). Participants were split up in four personality groups: Type D (34,9%), negative affectivity (23,4%), social inhibition (13,4%), and a reference group (28,3%) (see Figure 1). There were no significant differences between the four personality types in sex, age or marital status. However, the outcomes did show trends (p <.10) for both sex and marital status (see Table 1). Testing Assumptions

9 TYPE D PERSONALITY AND PERCEIVED STRESS 9 The assumption of normality for the perceived stress scores was satisfied for all personality types as assessed by Shapiro-Wilk's test (p >.05). There were no missing values, although two outliers were apparent within the data, as assessed by cases with standardized residuals greater than ±3 standard deviations. The analyses were conducted both with and without outliers, but they did not affect the outcomes and were therefore not excluded from the study. There was homogeneity of variances for perceived stress, as assessed by Levene's test for equality of variances (p =.299). There was a linear relationship between perceived stress for each personality type, as assessed by visual inspection of a scatterplot. There was homogeneity of regression slopes as the interaction term for perceived stress and social support was not statistically significant, F(3, 205) = 0.91, p =.438. Standardized residuals for the personality types and the overall model were normally distributed, as assessed by Shapiro- Wilk's test (p >.05). There was homoscedasticity and homogeneity of variances for the covariate, as assessed by visual inspection of a scatterplot and Levene's test of homogeneity of variance (p =.438). However, the independent variable and the covariate were not independent due to a significant effect (p =.016) and correlation (r = -.26). Type D and Perceived Stress A one-way ANOVA was conducted to determine if the amount of perceived stress (PSS score) differed between the four personality types. This analysis showed that the differences in PSS score between the personality types were statistically significant, F(3, 205) = 24.53, p <.001, η 2 =.26 (see Table 2). Due to no equal sample sizes between the personality groups, Tukey/Kramer post hoc test was used to interpret the outcomes. The post hoc analysis revealed that the reference group (M = 14.15, SD = 4.76) scored significantly lower on perceived stress compared to the negative affectivity group (M = 19.22, SD = 5.02), F = 27.61, p <.05 and the Type D group (M = 20.34, SD = 5.45), F = 50.11, p <.05. In addition, the social inhibition group (M = 13.54, SD = 4.10) also scored significantly lower on

10 TYPE D PERSONALITY AND PERCEIVED STRESS 10 perceived stress compared to the negative affectivity group (M = 19.22, SD = 5.02), F = 23.11, p <.05 and the Type D group (M = 20.34, SD = 5.45), F = 37.59, p <.05 (see Table 2, Table 3, and Figure 2). Type D and Social Support A one-way ANOVA was conducted to determine if the amount of perceived social support (MSPSS score) was different between the personality types. The MSPSS score was statistically significantly different between the four groups, F(3, 205) = 7.09, p <.001, η 2 =.09 (see Table 1). A Tukey/Kramer post hoc test, for analyzing unequal sample sizes, revealed that the reference group (M = 71.02, SD = 11.45) scored significantly higher on perceived social support compared to the Type D group (M = 63.45, SD = 13.13), F = 14.43, p <.05. The negative affectivity group (M = 71.16, SD = 7.88) scored significantly higher on perceived social support as well in comparison to the Type D group (M = 63.45, SD = 13.13), F = 13.37, p <.05. In addition, the negative affectivity group (M = 71.16, SD = 7.88) scored significantly higher on perceived social support than the social inhibition group (M = 64.89, SD = 11.77), F = 5.37, p <.05. Furthermore, a trend was visible, showing that the reference group (M = 71.02, SD = 11.45) also nearly scored significantly higher on perceived stress than the social inhibition group (M = 64.89, SD = 11.77), F = 5.46, p =.052 (see Table 2, Table 4, and Figure 3). Mediating Effect of Social Support An ANCOVA analysis was used to determine the effect of personality type on perceived stress after controlling for perceived social support. There was a small significant effect of the covariate social support on the relationship between personality type and perceived stress, F(1, 204) = 5.88, p =.016, r = -.20, partial η 2 =.03. After adjustment for perceived social support, there was a statistically significant difference in perceived stress between the different personality types, F(3, 204) = 23.20, p <.001, partial η 2 =.25. A post

11 TYPE D PERSONALITY AND PERCEIVED STRESS 11 hoc analysis was performed with a Bonferroni adjustment and revealed that the reference group (M = 14.40, SE =.65) scored significantly lower on perceived stress compared to the negative affectivity group (M = 19.49, SE =.71), F = 28.39, p <.001 and the Type D group (M = 20.04, SE =.59), F = 39.74, p <.001. In addition, the social inhibition group (M = 13.34, SE =.94) did also score significantly lower on perceives stress compared to the negative affectivity group (M = 19.49, SE =.71), F = 26.92, p <.001 and the Type D group (M = 20.04, SE =.59), F = 37.25, p <.001 (see Table 2, Table 5, and Table 6). Discussion The aim of the current study was to investigate the relationship between Type D personality and perceived stress and whether this relationship is mediated by social support. The first hypothesis was that Type D personalities would experience more perceived stress than the other three personality types. The second hypothesis was that the differences between personality types would diminish when controlled for social support. The results of the demographic analyses showed no differences between the four personality types on sex, age or marital status, but there were trends visible for both sex and marital status. Additionally, the analyses showed that the groups with negative affectivity (i.e. the negative affectivity and the Type D group) scored higher on perceived stress than those without negative affectivity (i.e. the reference and the social inhibition group). These outcomes do not support the first hypothesis predicting that solely the Type D personality would experience higher perceived stress. The results also showed that the groups with social inhibition (i.e. the social inhibition and the Type D personality group) scored lower on social support than the group with negative affectivity. In addition, the results showed a near to significant lower score in social support for the social inhibition group compared to the reference group. The results thus showed an effect of negative affectivity on perceived stress and an effect of social inhibition on social support.

12 TYPE D PERSONALITY AND PERCEIVED STRESS 12 These findings might imply that instead of an interaction effect of negative affectivity and social inhibition, as assumed in Type D personality, the traits have independent effects on perceived stress and social support. These outcomes are in line with the research done by Watson and Clark (1984), which showed that those scoring high on negative affectivity experience more stress than those without. They are also in line with the research of Denollet (1997, 2005) which showed that those scoring high on social inhibition actively push away social support. Furthermore, the found separate effects of negative affectivity and social inhibition on perceived stress and social support, may explain the lack of independence between the covariate and the independent factor in the analyses. As expected, the findings showed a small mediating effect of social support on the relationship between personality type and perceived stress. This mediating effect is consistent with the buffering hypothesis, which described that higher social support would lower the amount of stress (Chao, 2011, 2012; Cohen & Wills, 1985; Schwarzer & Leppin, 1989). These findings do not support the research of Polman et al. (2010), which showed that social support did not have any significant mediating effect on the relationship between Type D and emotional distress. However, the results still displayed the same differences between the personality types as before adjustment for social support. Hence there are no indications that the mediating effect of social support is persuasive enough to alleviate the effect of Type D personality and negative affectivity on perceived stress. These results could therefore not support the second hypothesis stating that the effect of personality type on stress would differ after adjusting for social support. These findings do also not support the research of Williams and Wingate (2012), which showed that social support mediated both directly and indirectly the effect of Type D on perceived stress. This could indicate that heightening social support might not be able to lower stress for people with the negative affectivity trait enough to lessen

13 TYPE D PERSONALITY AND PERCEIVED STRESS 13 the prevalence of emotional distress-related CHD patients and other stress-related health issues. Despite these outcomes, there may not be concluded that the buffering hypothesis cannot be used to lessen the progression and mortality of CHD. The current study, as well as the research by Williams and Wingate (2012), only showed the buffering hypothesis in a noncardiac population, which might not generalizable to a cardiovascular population. Further research is required to investigate whether social support can mediate the relationship between negative affectivity and stress in CHD-patients. The current study has several limitations: First, the research population was small (with unequal sample sizes between the groups), selected through convenience sampling, and not based on a nationwide sample. This might limit the generalizability towards a more general population. Second, only self-report measures have been used to obtain the data. The MSPSS questionnaire only assesses the amount of social support, but not the quality, which might affect the mediation on stress. Moreover, college students appear to give more homogeneous answers in self-report measures than non-student populations and the effect sizes between student and non-student populations are found to be different in both direction and magnitude, without any systemic pattern (Peterson, 2001). This is reason to be cautious with generalizing the findings towards other populations. For future research, it would be recommended to use more objective methodologies, such as qualitative research, to assess social support and perceived stress. Third, a student s life is more uncontrollable and unpredictable and therefore more stressful than for non-students due to multiple social, academic, and emotional stressors (Chao, 2011, 2012; Ross, Niebling, & Heckert, 1999; Stoliker, & Lafreniere, 2015). However, university environment, family troubles, and other possible confounding variables, such as

14 TYPE D PERSONALITY AND PERCEIVED STRESS 14 alternative personality factors or depression, were not considered in the current study. Coping strategies were also not included in the analyses, even though students assess and cope with stressful situations in many ways, which might indicate that people of different populations have other perceptions and reactions to stress (Chao, 2011). Besides, those with negative affectivity or social inhibition might use typical or different coping styles than others, which could result in different experiences of stress as well. It would be advisable to consider more and different variables in future research. In addition, the marital status in a student population might often not be as evolved as it would be at a later age: Students generally have less serious and more short-term relationships (Chao, 2011, 2012). This is in line with the findings of the current study, which showed no differences in marital status between the personality groups. Nevertheless, a trend was found in the analyses, indicating that those with social inhibition might have relationships less often than those without (see Table 1). Future research with a larger and more diverse population might perhaps show more differences between the personality types on demographics. Lastly, students often have no long-term friendships yet, due to switching schools and their regular changing living situation (Ross et al., 1999). Together with the short-term relationships, this might indicate that most of the students social support would exist from close family, such as parents and siblings. These family relations could give students, still living with their parents or only just moved out, a secure feeling, which might explain the relatively high perceived social support found in the current study. However, the study of Cohen and McKay (1984), described that the buffering effect of certain social support might only be effective for relevant stressful conditions and experiences. This could indicate that the support of parents is only effective for family related stress, but not for buffering the study

15 TYPE D PERSONALITY AND PERCEIVED STRESS 15 related stress the students might have in the current study. This may have influenced the results. Although the use of undergraduate students might limit the external validity due to the mentioned effects, it also has certain benefits. For example, students are easily accessible and cheap participants in the current study they participated in exchange for participation credits (needed for their study) instead of money. They are also more often used in research, which makes these studies easier to compare. In addition, the multiple significant results and trends, which were found in the current study s student population, may imply that it could be rewarding to do more research with larger and more diverse populations. Another benefit of the current study is that it has extended the evidence on the buffering hypothesis and Type D personality. It has also given more theories about the effects of negative affectivity and social inhibition on Type D personality. These effects could indicate that studies and interventions for emotional-distress related CHD should perhaps focus more on negative affectivity, next to Type D personality. In addition, the current study has supplemented previous research on the present topic, which was limited. The absence of more previous research on the topic may be explained due to publications overlooked by the researcher (retrieval bias), or because some findings may not have been published due to rejections by journal publishers (publication bias) or may not have been submitted (reporting bias). In total, further research is required to be able to generalize towards a more general population. This would preferably be done with a more nationwide, non-student population and with the use of more objective methodologies. Perhaps also other variables can be considered in future studies, such as coping strategies, other personality traits, and whether the source and quality of social support matters. Because only a small effect was found in the current study to support the buffering hypothesis for Type D personalities, more research into

16 TYPE D PERSONALITY AND PERCEIVED STRESS 16 this topic is advisable as well. Perhaps psychosocial interventions could be used to enhance the amount of social support and to test whether this can strengthen the effect of the buffering hypothesis. This could possibly be done in a study with a cardiac population as well to discover if it may reduce the progression and the mortality of emotional distress-related CHD. In addition, it would be advisable to study in what other ways the amount of stress can be lessened in those with the negative affectivity trait, to reduce the prevalence of CHD and other stress-related health issues. Moreover, based on the current findings it is recommended to do more future research with the four personality types instead of only Type D and nontype D personality, to discover more about both the separate and the interaction effect(s) of social inhibition and negative affectivity. Conclusion The current study aimed to investigate the relationship between Type D personality and perceived stress and the mediating effect of social support. The hypothesis that Type D personality would have more perceived stress than the other personality types was not supported by the results. The hypothesis that the effect of Type D on stress would no longer be apparent when controlled for social support, was also not supported by the current study. The results did support the buffering hypothesis by showing a significant mediating effect of social support. However, the findings were not in line with any previous research on the effect of social support on the relationship between Type D personality and perceived stress. There were several limitations to the study, such as a small sample size, convenience sampling, and self-report measures, which might result in a lower external validity. Furthermore, using students as participants had both negative aspects (i.e. less generalizability due to homogeneous answers and demographics) and positive aspects (i.e. easier comparable, cheaper and more accessible). The findings of the current study were beneficial by supporting previous theories and extending the existing evidence on the topic. The found effects and

17 TYPE D PERSONALITY AND PERCEIVED STRESS 17 trends suggest that effects might be found within a larger and more diverse population as well. Unexpected findings were that negative affectivity and social inhibition showed separate effects on perceived stress and social support instead of an interaction effect. Further research is recommended to discover what can alleviate stress in different populations (i.e. in both cardiac and non-cardiac populations) to lessen stress-related health issues and prevalence, progression, and mortality for emotional distress-related CHD. Further research into the effect of the buffering hypothesis for Type D personalities is also recommended, as well as researching the separate and the interaction effects of social inhibition and negative affectivity.

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22 TYPE D PERSONALITY AND PERCEIVED STRESS 22 Appendix Table 1 Demographics of sex, age, and marital status for all four personality types Total (N=209) Reference (N=59) SI (N=28) NA (N=49) Type D (N=73) Test statistic P Sex (female) 76.6% (160) 69.6% (41) 64.3% (18) 85.7% (42) 80.8% (59) * Age mean (SD) 20.3 (2.08) 20.6 (2.46) 20.6 (2.26) 20.3 (2.17) 20.0 (1.51) Marital status (relationship) 42.1% (88) 44.1% (26) 28.6% (8) 55.1% (27) 36.9% (27) * Note. SD = Standard Deviation, SI = Social Inhibition, NA = Negative Affectivity, *p <.10.

23 TYPE D PERSONALITY AND PERCEIVED STRESS 23 Table 2 Differences in perceived stress and perceived social support for all four personality types Total (N=209) Reference (N=59) SI (N=28) NA (N=49) Type D (N=73) ANOVA M SD M SD M SD M SD M SD F df p Perceived Stress , 205 <.001 Perceived Social Support , 205 <.001 Note. M = Mean, SD = Standard Deviation, SI = Social Inhibition, NA = Negative Affectivity, df = degrees of freedom.

24 TYPE D PERSONALITY AND PERCEIVED STRESS 24 Table 3 Increases between personality groups on perceived stress scores Negative Affectivity Type D From Increase F p Increase F p Reference < <.05 Social Inhibition < <.05 Note. P-values were established through Tukey/Kramer post hoc test, due to unequal sample sizes, and are therefore not exact.

25 TYPE D PERSONALITY AND PERCEIVED STRESS 25 Table 4 Decreases between personality groups on social support scores Social Inhibition Type D From Decrease F p Decrease F p Reference * <.05 Negative Affectivity < <.05 Note. P-values were established through Tukey/Kramer post hoc test, due to unequal sample sizes, and are therefore not exact. *p <.10, showing a trend.

26 TYPE D PERSONALITY AND PERCEIVED STRESS 26 Table 5 Differences between personality groups on perceived stress scores after adjusting for social support Negative Affectivity Type D From Increase F p Increase F p Reference < <.001 Social Inhibition < <.001 Note. P-values were established through a Bonferroni correction.

27 TYPE D PERSONALITY AND PERCEIVED STRESS 27 Table 6 Adjusted and unadjusted intervention means and variability for Perceived Stress with Perceived Social Support as a covariate Unadjusted means Adjusted means Group N M SE M SE Reference Social Inhibition Negative Affectivity Type D Note. N = number of participants, M = Mean, SD = Standard Error.

28 TYPE D PERSONALITY AND PERCEIVED STRESS 28 High SI Low SI High NA Type D group Negative Affectivity group Low NA Social Inhibition group Reference group Figure 1. The 2-by-2 Type D taxonomy as used in the current study to distinguish the four different personality groups. NA = Negative Affectivity; SI = Social Inhibition.

29 TYPE D PERSONALITY AND PERCEIVED STRESS 29 Figure 2. Differences in Perceived Stress between the personality Types. PSS = Perceived Stress Score; Ref. = Reference group, SI = Social Inhibition; NA = Negative Affectivity.

30 MSPSS-score TYPE D PERSONALITY AND PERCEIVED STRESS 30 Perceived Social Support Ref. SI NA Type D Figure 3. Differences in Perceived Social Support between the personality types. MSPSS = Multidimensional Scale of Perceived Social Support; Ref. = Reference group; SI = Social Inhibition; NA = Negative Affectivity.