What Is Your Risk for Clinical Depression after Disasters?

Overview

Disasters have a major impact on individuals and society, increasing over time, and summarized here by the United Nations Office for Disaster Risk Reduction. Psychiatric research in disasters has focused on posttraumatic stress disorder (PTSD), and therefore the data for PTSD is clearer, but there has been less attention to depression and other conditions. In order to better understand predictors of major depressive disorder (MDD), Carol North and colleagues (2017) conducted a methodologically sound review of multiple disaster survivor clinical databases to better understand risk factors for depression following disasters.

They note that rates of PTSD following disasters averages around 20 percent, with highest rates up to 35 percent following the most severe disasters. MDD rates by contrast range from 13 to 31 percent, in a review of 5 studies (Salguero, Fernandez-Berrocal, Iruarrizaga, et al, 2011). In discussing their findings, the authors pointed to the need for future research to better define the risk factors for depression following disasters. Another open line of inquiry is whether there are higher rates of pathology following terrorist events, versus other disasters.

While some researchers have suggested that terrorism results in high rates of PTSD than non-terrorist disasters, other studies have been inconclusive. To date, reliable predictors for PTSD include prior pathology and female gender, with weaker findings for risk associated with severity of exposure, physical injury during the event, youth, marital status, minority status, lower socioeconomic status, lower social support and maladaptive coping, typically avoidant. The understanding of post-disaster MDD is less developed.

The current study

To address this gap in knowledge, North, Baron and Chen (2017) used two disaster databases which had been developed using a consistent statistical approach including structured diagnostic interviews, more reliable than self-report instruments. One database includes 808 survivors directly exposed to all kinds of disaster, including natural disasters, intentional attacks including murder and bombing, and accidents such as aviation disasters and fires. The second database includes 373 survivors of the 9/11 WTC attacks in New York City, including those with direct and indirect exposure to the disaster. Together, they covered a span of time from shortly after the disaster to up to 6 months post-disaster.

All participants were interviewed using the Diagnostic Interview Schedule, which is used with regularly by many disaster researchers as a reliable and valid tool looking at demographic variables, MDD, PTSD, panic disorder, generalized anxiety disorder and alcohol and chemical dependency disorders. The data were analyzed looking at the 11 total different disasters using a hierarchical multivariate logistical regression model to identify significantly associate variables and interactions between pairs of variables. The general model used for the 808 person 10 disaster database was used in the analysis of the WTC attacks to determine overall predictive factors for MDD as a function of significant variables.

Findings

Three major factors were found to be independent predictors of post-disaster Major Depressive Disorder in the larger 10 disaster database: pre-disaster major depression, indirect exposure to the disaster via close friends and family, and disaster-related PTSD. In the 9/11 WTC sample, five factors were found to be independent risk factors for MDD: unmarried status, indirect exposure, pre-disaster major depression, disaster-related PTSD and injury during the disaster. The findings for the two databases were cross-checked against each other to confirm the final model, with the following four factors predictive of MDD following disaster:

1. Terrorist incident
2. Pre-disaster lifetime MDD
3. Indirect exposure via friends and family
4. Disaster-related PTSD

The influence of the factors in each database was as follows: for the 10 disaster database, the risk of MDD was 2 percent with no factor, 12 percent with more than one factor, 47 percent with more than two factors, and 94 percent with three or more factors. For the 9/11 WTC database, the risk was 7 percent with zero factors, 55 percent with more than one factor, 73 percent with more than two, and 80 percent with three.

Implications

These results, from a larger data set using a comprehensive analysis, are significant in general as they extend our understanding and clarify prior findings. Notably, post-disaster Major Depressive Disorder is associated with type of disaster—terrorism—in contrast to findings for PTSD being unrelated to type of disaster. Second, and importantly, demographic variables including age, marital status, gender, ethnicity and socioeconomic status were not associated with risk of Major Depressive Disorder following disaster exposure, although they were present as predictive factors during an initial part of the data analysis which were not significant in the final model. It would be interesting to know whether well-controlled Major Depressive Disorder is less of a risk factor than people who are symptomatic at the time of the disaster.

Understanding risk factors will help to identify at-risk sub-populations for future disaster response, in order to 1) planfully allocate scarce resources to those with greatest need and 2) avoid unnecessarily, and possibly harmfully, screening low-risk groups best addressed as being likely to have non-pathological responses. Understanding risk factors is important for mitigating post-disaster pathology, and for improving preparation in-between disasters to protect vulnerable groups and prevent pathological reactions, when possible.