Sample characteristics
The mean ± SD age of the 500 caregivers was 50.2 ± 13.1 years; females represented 65.3% (n = 345), and those of Caucasian heritage represented 87.8% (n = 439) of the sample. There were 188 (37.6%) parental caregivers and 182 (36.4%) spousal caregivers. The mean ± SD age of the 500 patients was 39.9 ± 13.5 years; females represented 56.2% (n = 281), and age of onset of illness was 16.02 ± 3.7 years. Patients’ mean ± SD GAF scores were 66.3 ± 11.5. Additional caregiver and patient characteristics are shown in .
Sample sizes for caregiver/patient pairs for the longitudinal analyses are given in . Although more than 80% (n = 400) of caregivers had follow-up data for general health and CES-D scores, only 60% and 67% (n = 300 and 335, respectively) of patients had 6- and 12-month SI and SUM-D scores, respectively. Since both patients’ and caregivers’ scores were needed for these analyses, we explored characteristics that were associated with caregivers’ and patients’ dropout. Lower patient education and the presence of prior suicide attempts both predicted patients’ dropout (p < 0.05). Higher baseline patients’ SI and depression (p < 0.05), as well as higher baseline caregivers’ depressed mood (p < 0.05), were significantly associated with caregivers’ dropout.
| Table 2Longitudinal analysis of caregiver health and depression: patient symptoms as time-varying covariate |
Caregiver health
Consistent with our hypotheses, mixed-effects linear modeling of patients’ SI as a time-varying covariate with caregivers’ health scores demonstrated that patients with higher SI at baseline and 6 and 12 months were associated with poorer caregivers’ health (lower scores) at baseline and 6 and 12 months, respectively, compared to patients with lower SI at each time point (, Model 1) [F(1,764 = 5.28, p = 0.02]. This relationship was significant even after controlling for patients’ history of suicide attempts [F(1,456) = 5.39, p = 0.02], education [F(1,456) = 7.74, p < 0.01], baseline GAF scores [F(1,456) = 7.85, p < 0.01], current alcohol or substance abuse [F(1,764) = 0.13, p = 0.72], and whether the patients lived with the caregivers [F(1,456) = 5.96, p = 0.02].
Moreover, mixed-effects linear modeling showed that patients whose SI increased from baseline at 6 and/or 12 months were associated with caregivers reporting poorer health at 6 and 12 months, compared to caregivers of patients with no increase in SI [F(1,335) = 11.56, p < 0.01], after controlling for baseline caregivers’ health [F(1,415) = 374.75, p < 0.01] and baseline patients’ SI [F(1.415) = 0.00, p = 0.99] (, Model 1a). This relationship was significant even after controlling for patients’ education [F(1,415) = 12.06, p < 0.01], living situation [F(1,415) = 6.93, p < 0.01], baseline GAF scores [F(1,415) = 3.48, p = 0.06], and current alcohol or substance abuse [F(1,335) = 0.10, p = 0.75]. Thus, caregiver self-reported health was consistently correlated with patients’ SI over time.
In contrast to the results for patients’ SI, separate analyses found that patients’ depression (SUM-D) scores at baseline, 6 months, and 12 months were not significantly related to caregivers’ self-reported health at baseline, 6 months, and 12 months, respectively [F(1,572) = 0.14, p = 0.71] (, Model 2), nor were changes in patients’ depression scores related to caregivers’ health at 6 and 12 months, after adjusting for baseline caregivers’ health and baseline patients’ depression [F(1,221) = 0.53, p = 0.47] (, Model 2a). Thus, SI appears to have contributed to caregivers’ health, whereas depression in the absence of SI did not.
Caregiver depression scores
Consistent with our hypothesis, a mixed-effects longitudinal model with patients’ SI as a time-varying covariate revealed that patients with greater SI at baseline and 6 and 12 months were associated with caregivers with higher CES-D depression scores at baseline, 6 months, and 12 months, respectively (, Model 3) [F(1,722) = 4.91, p = 0.03], even after controlling for previous patients’ suicide attempts [F(1,452) = 0.62, p = 0.43], patients’ education [F(1,452) = 2.88, p = 0.09], GAF scores [F(1,452) = 7.44, p < 0.01], current alcohol or substance abuse [F(1,722) = 0.66, p = 0.42], and patients’ living situation [F(1,452) = 4.91, p = 0.03]. However, increase in patients’ SI from baseline was not significantly associated with caregivers’ CES-D depressive scores at 6 and 12 months [F(1,301) = 1.35, p = 0.25] after controlling for baseline caregivers’ depression [F(1,389) = 391.84, p < 0.01] and baseline patients’ SI [F(1,389) = 0.78, p = 0.38] (Model 3a).
Consistent with our hypothesis, higher patient depression (SUM-D) scores at baseline, 6 months, and 12 months were associated with higher caregivers’ depression at baseline, 6 months, and 12 months, respectively [F(1,542) = 5.31, p = 0.02] (, Model 4), even after controlling for patients’ previous suicide attempts [F(1,453) = 0.59, p = 0.44], patients’ education [F(1,453) = 1.31, p = 0.25], GAF scores [F(1,453) = 6.53, p = 0.01], current alcohol or substance abuse [F(1,542) = 1.28, p = 0.26], and patients’ living situation [F(1,453) = 4.52, p = 0.03]. Change in patients’ depression from baseline was marginally associated with caregivers’ depression at 6 and 12 months [F(1,302) = 3.29, p = 0.07] after controlling for baseline caregivers’ depression [F(1,390) = 419.6, p < 0.01], baseline patients’ depression [F(1,390) = 2.03, p = 0.15], previous suicide attempts [F(1,390) = 2.09, p = 0.15], patients’ education [F(1,390) = 0.27, p = 0.60], GAF scores [F(1,390) = 0.00, p = 0.96], current alcohol or substance abuse [F(1,302) = 0.21, p = 0.65], and patients’ living situation [F(1,390) = 1.07, p = 0.30] (Model 4a).