Incidence and risk factors for post-traumatic stress disorder in a population affected by a severe flood

We aimed to study the risk of developing post-traumatic stress disorder (PTSD) symptoms in people who resided in an affected area by an extremely severe flood, and sociodemographic risk factors associated with this condition.

A geographic information system (GIS) was used to distribute the rainfall data. A case-control study was developed to study the relationship between PTSD and sociodemographic risk factors.

To delineate the areas affected by the flood and the intensity of this rainfall in comparison with historical hydrological data, we employed geographical information systems (GIS). Then, we recruited a representative sample of the affected population and another population sample that lived at the time of this disaster in adjacent geographical areas that were not affected. Both groups were randomly selected in primary care practices, from December 1st 2012 to January 31st 2013. All participants, 70 from the affected areas and 91 from the non-affected, filled a sociodemographic questionnaire and the trauma questionnaire (TQ) to identify and rate PTSD symptoms.

Our GIS analysis confirmed that the amount of precipitation in 2012 in the areas affected by the flood was exceptionally high compared with historical average rainfall data (461l per square metre vs 265). Individuals who resided in the affected areas at the time of the flood were at much higher risk of developing PTSD symptoms (OR: 8.18; 95% CI: 3.99-17.59) than those living in adjacent, non-affected localities. Among the sociodemographic variables included in this study, only material and financial losses were strongly associated with the onset of PTSD (P < 0.001). Physical risk during this life-threatening catastrophe also indicated a positive correlation with later development of PTSD symptoms; however, it did not reach statistical significance (P = 0.06).

Populations affected by severe floods may suffer an increase of PTSD symptoms in the following months. This finding, along with the importance of material losses as a predictor for such disorder, may help develop effective plans to minimize the negative impact of these natural disasters on public health.