Trends in DSM-IV anxiety-mood disorders and suicidality
The estimated prevalence of any anxiety-mood disorder did not change significantly between the baseline survey (30.7%) and the follow-up survey (33.9%; t = 1.9, p = .06), although the trend is positive. () The estimated prevalence of SMI, in comparison, is significantly higher in the follow-up than baseline survey in the total sample (14.0% vs. 10.9%, t = 2.4, p = .018) as well as in the sub-sample of respondents who are not from the New Orleans Metropolitan Area (13.2% vs. 9.4%, t = 2.1, p = .038). This trend is not significant, in comparison, in the New Orleans Metro sub-sample (16.9% vs. 16.5%, t = 0.1, p = .91). The estimated prevalence of PTSD is significantly higher in the follow-up than baseline survey in the sub-sample exclusive of New Orleans Metro (20.0% vs. 11.8%, z = 4.0, p < .001), but not in the New Orleans Metro sub-sample (24.1% vs. 25.9%, t = 0.4, p = .68). The prevalence of suicidality, finally, is significantly higher in the follow-up than baseline survey both with regard to suicidal ideation (6.4% vs. 2.8%, t = 2.3, p = .020) and suicide plans (0.8% vs. 0.2%, t = 2.0, p = .044). These trends, unlike those for SMI and PTSD, are significant and relatively comparable in magnitude in both the New Orleans Metro sub-sample and in the remainder of the sample.
Trends in the estimated prevalence of DSM-IV anxiety-mood disorders (in the 30 days before interview) and suicidality (in the 12 months before interview) in the two surveys
We cross-classified baseline and follow-up diagnoses in order to study the composition of the diagnoses with significant trends. The majority of respondents classified as having SMI at follow-up either already had SMI at baseline (39.9%) or progressed from baseline MMI (31.6%) to SMI, while the remaining 28.5% represent delayed onsets (i.e., no MMI at baseline). (, Part I) A similar pattern exists for PTSD, where the majority of follow-up cases either already had PTSD at baseline (41.7%) or progressed from baseline MMI or SMI to PTSD (27.1%), while the remaining 31.2% are delayed onsets (i.e., no MMI or SMI at baseline). The proportions of delayed onsets are comparable for suicidal ideation (24.1%) and somewhat higher for suicide plans (46.6%), while the proportions with persistence (16.6% and 26.0% for ideation and plans, respectively) are lower than for SMI and PTSD. The proportions that represent progressions (i.e., from baseline cases with MMI and SMI) are higher for suicidal ideation (59.3%) than for SMI or PTSD and comparable for suicide plans (27.4%) compared to SMI and PTSD.
Decomposition of estimated prevalence of DSM-IV SMI and PTSD and suicidality between the two surveys (n = 815)
It is noteworthy that the majority of respondents with baseline SMI (51.1%) continued to have SMI at follow-up, while 30.8% improved (i.e., were classified as having MMI at follow-up) and only a relatively small minority (18.1%) recovered (i.e., no longer met criteria either for SMI or MMI). (, Part II) In the case of PTSD, 70.4% of baseline cases continued to have PTSD at follow-up, while an additional 10.3% were classified as having MMI or SMI but not PTSD at follow-up, and only 19.3% recovered. Persistence was somewhat lower for suicidal ideation (37.9%), but much higher for plans (69.8%). Improvement, in comparison, was comparatively high for suicidal ideation (49.9%), but not for suicide plans (16.0%). Recovery (i.e., no MMI, SMI, or suicidality at follow-up), finally, was relatively uncommon for either suicidal ideation (12.2%) or plans (18.0%).
Socio-demographic predictors of the trends
Only three of the socio-demographic variables are significant predictors of trends in SMI, PTSD, or suicidal ideation: respondent age, family income, and current living situation. () (Suicide plans, which also increased significantly over time, were too rare to be included in the trend analysis.) Respondent age significantly predicts increased prevalence of PTSD (highest increases among respondents ages 40-59) and suicidal ideation (highest increases among respondents ages 18-39). Low family income predicts increased prevalence of all three outcomes. Family living situation predicts increased prevalence of SMI (higher increases among respondents not living in the same town as before the hurricane, whether or not they live in the same county-parish or state, compared to those living in the same town, whether or not they live in the same house). While significant in statistical terms, these associations are not strong in substantive terms. The significant odds-ratios (in the range 3.5-5.7) explain only between 2.1% (PTSD) about 2.7% (SMI) of the variance in the outcomes based on Phi-square tests.
The effects of socio-demographic variables in predicting trends in estimated DSM-IV SMI and PTSD and suicidal ideation in the panel sample (n = 815)1
An attempt was made to distinguish the predictors of delayed onset from the predictors of persistence by including interactions between the predictors and the baseline measures of the outcomes in an expanded version of the prediction equations, but none of these models conversed due to the sparseness of the data. As a result, we cannot determine whether the significant socio-demographic predictors are predicting delayed onsets of the outcomes, persistence, or both.
The effects of hurricane-related stress
One possible explanation for the significant increases in the prevalence estimates of SMI, PTSD, and suicidal ideation is that hurricane-related stresses might have increased over time due to the slow pace of recovery efforts. As it turns out, though, this is not the case. A significantly lower proportion of respondents reported hurricane-related stress in the follow-up survey (57.5%) than in the baseline survey (91.7%; t = 10.2, p < .001). () This significant decrease exists both in the New Orleans Metro sub-sample (97.9% vs. 78.3%, t = 8.0, p < .001) and in the remainder of the sample (90.0% vs. 51.7%, t = 8.2, p < .001). The decrease exists not only for stress overall but also for severe stress (32.6% vs. 13.2%, t = 5.4, p < .001) and serious stress (27.6% vs. 12.9%, t = 4.7, p < .001). It is noteworthy, in light of the fact that the SMI-PTSD increases exist only in the sub-sample exclusive of the New Orleans Metro Area, that the decrease in hurricane-related stress is less pronounced in New Orleans Metro than the remainder of the sample. Indeed, the prevalence of stress in the follow-up survey is significantly higher in the New Orleans Metro sub-sample than in the remainder of the sample (78.3% vs. 51.7%, t = 6.1, p < .001). This means that higher levels of residual hurricane-related stress cannot explain the fact that SMI-PTSD prevalence increased over time only among respondents not from the New Orleans Metro Area.
The prevalence of hurricane-related stress in the two surveys
Another possibility is that the psychological effects of hurricane-related stresses increased over time even though the magnitude of the stresses themselves decreased. A comparison of the cross-sectional associations between hurricane-related stresses and the outcomes finds some superficial support for this possibility with regard to SMI, as the odds-ratios linking stress with SMI in the follow-up survey are consistently larger than the parallel odds-ratios in the baseline survey. () However, these differences are not statistically significant (χ24 = 8.1, p = .09). Furthermore, the pattern is not less pronounced in the New Orleans Metro sub-sample than in the remainder of the sample (χ24 =5.1, p = .28; detailed results available on request) This means that heightened reactivity to hurricane-related stress cannot explain the fact that the significant increase in SMI is confined to respondents in the sub-sample exclusive of the New Orleans Metro Area. Furthermore, the pattern of higher odds-ratios at follow-up than baseline does not hold either for PTSD or for suicidal ideation. In the case of suicidal ideation, the rarity of the outcome required the stress measures to be dichotomized (severe stress vs. all others) to stabilize parameter estimates.
The cross-sectional associations of hurricane-related stresses with estimated DSM-IV SMI and PTSD and suicidal ideation (n = 815)1
The model was expanded to study the effects of hurricane-related stress on trends in SMI, PTSD, and suicidal ideation. This was done by adding a control for the baseline value of the outcome to the prediction equation along with measures of stress assessed in both surveys. Baseline stress was not a significant predictor of trends in either SMI (χ24 = 4.3, p = .37) or PTSD (χ24 = 8.0, p = .09), while stress at follow-up was significant in both equations (χ24 = 31.5, p< .001; χ24 = 13.0, p = .011). No significant interactions were found between baseline stress and follow-up stress or between sub-sample (i.e., New Orleans Metro vs. the remainder of the sample) and either measure of stress. (Detailed results available on request.) Based on these results, the final model for trends in SMI and PTSD included stress in the follow-up sample as the only key predictor. () Stress exposure in this model is associated with substantial variation in both SMI and PTSD at follow-up, with odds-ratios for serious-severe stress in the range 35.8-42.2 for SMI and 12.8-20.3 for PTSD after controlling for baseline SMI and socio-demographics.
The effects of hurricane-related stresses in predicting trends in estimated DSM-IV SMI and PTSD and suicidal ideation in the panel sample along with standardized prevalence estimates of the outcomes (n = 815)1
A good way to grasp the substantive significance of these results is to examine standardized prevalence estimates of the outcomes SMI and PTSD at follow-up. The latter are prevalence estimates in which adjustments have been made to correct for the associations of stress with baseline values of the outcomes, socio-demographics, and sub-sample, so that the effects of stress can be seen distinct from the effects of these other variables. These standardized prevalence estimates are 0.3% SMI and 1.4% PTSD among respondents with no residual hurricane-related stress compared to 29.5-30.6% SMI and 38.8-46.1% PTSD among respondents with moderate-to-severe stress. If we think of these associations as causal, the population attributable risk proportions of SMI and PTSD due to hurricane-related stress (i.e., the proportions of currently existing SMI and PTSD that would be expected to remit if all hurricane-related stress was resolved) are 89.2% for SMI and 31.9% for PTSD.
The best-fitting model is different for suicidal ideation, as baseline stress and stress at follow-up (both dichotomized to severe-serious vs. all others due to the rarity of the outcome and the nonlinearity of the association with hurricane-related stress) interact in predicting trends in suicidal ideation (χ21 = 7.2, p = .007). The best-fitting model is one that distinguishes respondents with severe-serous hurricane-related stress in one or both surveys versus all others. An additional complication, though, is that the effect of stress in this model differs significantly between the New Orleans Metro sub-sample and the remainder of the sample (χ21 = 8.47.2, p = .007), with the odds-ratio substantially higher among respondents not from the New Orleans Metro Area (104.1) than from New Orleans Metro (2.2). The prevalence estimates of suicidal ideation at follow-up among respondents with severe-serious hurricane-related stress are 3.1% in the New Orleans Metro sub-sample and 13.0% in the remainder of the sample compared to 0.3% and 0.0% among respondents without severe hurricane-related stress. If we think of these associations as causal, the population attributable risk proportion of suicidal ideation associated with severe-serious hurricane-related stress is 61.6% in the total sample.