What this trial measures

• Hypothesis 1: There will be a main effect of self-affirmation condition on CV reactivity and recovery to the grief recall taskTwo months after the last participant data collection.

  A series of one-way ANCOVAs will be conducted to compare measures of cardiovascular reactivity and recovery between the self-affirmation and control conditions, controlling for gender, race, and baseline values, using a significance level of α = .05. CV reactivity will be operationalized as the difference between CV during grief recall and CV baseline measures. CV recovery will be operationalized as the difference between CV recovery measures and CV baseline measures.

• Hypothesis 2: Grief severity (as measured by the PG-13 Questionnaire) will moderate the effect of the self-affirmation condition on cardiovascular reactivity and recovery.Two months after the last participant.

  A series of multiple regression analyses will be conducted separately for HR, SBP, DBP and HF-HRV on reactivity and recovery. Predictor variables will include grief severity (PG-13 scores), experimental condition (value-affirmation vs. control, dummy-coded), and the condition x Grief Severity interaction. Dependent variables will be cardiovascular reactivity and recovery. A significant interaction would support the hypothesis that the effect of self-affirmation on reactivity and/or recovery is dependent on grief levels. It is predicted that the stress-buffering effect of self-affirmation will be strongest for individuals with high grief severity, evidenced by a smaller HR, SBP, and HF-HRV compared to the control group. The method calculating recovery would be the same as the method used in H1.

• Hypothesis 3 (Exploratory): There will be a mediated moderation effect: the self-report measurement of self-worth mediates the change in cardiovascular reactivity, moderated by grief severity.Two months after the last participant data collection.

  A moderated mediation analysis with Hayes PROCESS model will be conducted to explore whether the effect of value-affirmation on cardiovascular reactivity is mediated by changes in self-worth and moderated by grief severity. Change in self-worth will be operationalized by the difference in scores on the Self-Worth Questionnaire (SWQ) taken at timepoint 2 and 3 (right before and after the grief recall). The research team hypothesized that the self-worth variable will mediate the relationship between experimental condition and cardiovascular reactivity, with the relationship between self-worth and reactivity moderated by the participant's level of grief severity.

• Hypothesis 4-1: Grief is related to psychological stress among young adult grieving participants: depressionTwo months after the last participant.

  To test the hypothesis that grief severity is positively associated with participant's level of depression, a bivariate correlation will be conducted. Grief severity, as measured by scores on the prolonged grief (PG-13) questionnaire, will serve as the predictor variable. PG-13 includes 13 questions with a minimum value of 13 and a maximum value of 65, while higher value indicates higher level of grief. The outcome variable will be the scores of the Beck Depression Inventory (BDI). The BDI scale includes 21 questions with a minimum value of 0 and a maximum value of 63, where higher value indicates higher levels of depression. The research team proposed that participants scoring higher on PG-13 would also score higher in BDI, indicating greater vulnerability to depression.

• Hypothesis 4-2: Grief is related to psychological stress among young adult grieving participants: anxietyTwo months after the last participant.

  To test the hypothesis that grief severity is positively associated with participant's anxiety level, a bivariate correlation will be conducted. Grief severity, as measured by scores on the prolonged grief (PG-13) questionnaire, will serve as the predictor variable. PG-13 includes 13 questions with a minimum value of 13 and a maximum value of 65, while higher value indicates higher level of grief. The outcome variable will be the scores of the Generalized Anxiety Disorder-7 scale (GAD-7). The GAD-7 scale includes 7 questions with a minimum value of 0 and a maximum value of 21, where higher value indicates higher levels of anxiety. The research team proposed that participants scoring higher on PG-13 would also score higher in GAD-7, indicating greater vulnerability to anxiety.

• Hypothesis 4-3: Grief is related to psychological stress among young adult grieving participants: worriesTwo months after the last participant.

  To test the hypothesis that grief severity is positively associated with participant's worriness level, a bivariate correlation will be conducted. Grief severity, as measured by scores on the prolonged grief (PG-13) questionnaire, will serve as the predictor variable. PG-13 includes 13 questions with a minimum value of 13 and a maximum value of 65, while higher value indicates higher level of grief. The outcome variable will be the scores of the Penn State Worry Questionnaire (PSWQ). The PSWQ scale includes 16 questions with a minimum value of 16 and a maximum value of 80, where higher value indicates higher levels of worriness. The research team proposed that participants scoring higher on PG-13 would also score higher in PSWQ, indicating greater levels of worriness.

• Hypothesis 4-4: Grief is related to psychological stress among young adult grieving participants: perceived stressTwo months after the last participant.

  To test the hypothesis that grief severity is positively associated with participant's sleep quality, a bivariate correlation will be conducted. Grief severity, as measured by scores on the prolonged grief (PG-13) questionnaire, will serve as the predictor variable. PG-13 includes 13 questions with a minimum value of 13 and a maximum value of 65, while higher value indicates higher level of grief. The outcome variable will be the scores of the Perceived Stress Scale (PSS-10). PSS-10 scale includes 10 questions with a minimum value of 0 and a maximum value of 40, where higher value indicates higher levels of daily stress experienced within the last month. The research team proposed that participants scoring higher on PG-13 would also score higher in PSS, indicating greater levels of perceived stress.

• Hypothesis 4-5: Grief is related to psychological stress among young adult grieving participants: sleep qualityTwo months after the last participant.

  To test the hypothesis that grief severity is positively associated with participant's sleep disturbance, a bivariate correlation will be conducted. Grief severity, as measured by scores on the Prolonged Grief (PG-13) questionnaire, will serve as the predictor variable. PG-13 includes 13 questions with a minimum value of 13 and a maximum value of 65, while higher value indicates higher level of grief. The outcome variable will be the scores of the Pittsburgh Sleep Quality Index (PSQI). PSQI includes a mixture of likert-scale questions and short-answer questions that is transferrable to scores, with a minimum value of 0 and a maximum value of 21, where higher value indicates worst sleeping quality. The research team proposed that participants scoring higher on PG-13 would also score higher in PSQI, indicating greater levels of sleep disturbance.

• Hypothesis 4-6: Grief is related to psychological stress among young adult grieving participants: Post-traumatic Stress DisorderTwo months after the last participant.

  To test the hypothesis that grief severity is positively associated with participant's PTSD symptoms, a bivariate correlation will be conducted. Grief severity, as measured by scores on the Prolonged Grief (PG-13) questionnaire, will serve as the predictor variable. PG-13 includes 13 questions with a minimum value of 13 and a maximum value of 65, while higher value indicates higher level of grief. The outcome variable will be the scores of the PTSD Checklist for DSM-5 (PCL-5). PCL-5 includes 20 questions with a minimum value of 0 and a maximum value of 80, where higher value indicates higher PTSD symptoms. The research team proposed that participants scoring higher on PG-13 would also score higher in PCL-5, indicating greater levels PTSD symptoms.

• Hypothesis 5-1 (exploratory): Grief Severity is associated with meaning violationTwo months after the last participant.

  To test the hypothesis that grief severity is associated with higher meaning violation, linear regression will be conducted. Grief severity, as measured by scores on the prolonged grief (PG-13) questionnaire, will serve as the predictor variable. PG-13 includes 13 questions with a minimum value of 13 and a maximum value of 65, while higher value indicates higher level of grief. The outcome variable will be the scores of the Global Meaning Violation Scale (GMVS). GMVS includes 13 questions with a minimum value of 0 and a maximum value of 78, where higher value indicates higher levels meaning violation brought by the death event. The research team proposed that participants scoring higher on PG-13 would also score higher on GMVS, indicating higher level of meaning violation.

• Hypothesis 5-2 (exploratory): Grief Severity is associated with perceived inclusionTwo months after the last participant.

  To test the hypothesis that grief severity is associated with higher inclusion of others in one's self, a linear regression will be conducted. Grief severity, as measured by scores on the prolonged grief (PG-13) questionnaire, will serve as the predictor variable. PG-13 includes 13 questions with a minimum value of 13 and a maximum value of 65, while higher value indicates higher level of grief. The outcome variable will be the scores of the Inclusion of Others in the Self Scale (IOS). IOS includes 2 subscales, each with a minimum value of 0 and a maximum value of 7, where higher value indicates higher levels of inclusion of other person or other group members to the self.

• Hypothesis 5-3 (exploratory): Grief Severity is associated with complicated relationshipTwo months after the last participant.

  To test the hypothesis that grief severity is associated with complicated relationship, a linear regression will be conducted. Grief severity, as measured by scores on the prolonged grief (PG-13) questionnaire, will serve as the predictor variable. PG-13 includes 13 questions with a minimum value of 13 and a maximum value of 65, while higher value indicates higher level of grief. The outcome variable will be the scores of the Social Relationship Index (SRI). SRI includes short-answer questions and likert-scale selections, with a minimum value of 4 and a maximum value of 24, where higher value indicates more complicated relationship.