Prevalence and risk factors of posttraumatic stress disorder among survivors five years after the “Wenchuan” earthquake in China

All participants were recruited from Leigu Town with about 7,700 people. Most people in this community were originally native inhabitants of Leigu Town, a subordinate town of Beichuan County, which is the epicenter of the earthquake where 80% of the houses collapsed and more than 1,000 people died. Because Leigu Town was a severely afflicted area in the earthquake, almost all survivors received psychological aids after the earthquake. The survivors were the target population in this study, and were sampled from all household units in this community. A method of systematic sampling was adopted according to household unit doorplate number, and 730 families were selected. The sampling ratio was about 30%. Only one participant within a family was recruited for interview to ensure independence of study subjects, which is usually the household host if available. The inclusion criteria are as: (1) willing to participate, over 18 years old, clear consciousness and without language disorders; (2) experienced the Wenchuan earthquake in Beichuan county on May 12, 2008. The exclusion criteria include: (1) mental retardation, dementia, or any other major psychosis (e.g., schizophrenia, major depressive disorders, and severe mental disorders); (2) Failure to be reached after three household visits or refuse to be interviewed. If a sampled individual was unavailable, the next available individual was sampled. We have inquired the participant about the mental health before the earthquake. If they had similar symptoms such as depression, anxiety or another psychological problem, they would be excluded.

Since 2010, Community Health Service Center in China has set up a health care information system with data on all residents with major psychosis in the network of basic community public health care centers. The community health care information system maintains a list of residents with mental retardation, dementia, or any other major psychosis diagnosed by community doctors using questionnaires such as Mini-Mental State Examination (MMSE) and the General Health Questionnaire (GHQ-12). According to the list from the community health care information system, residents with mental retardation, dementia, or any other major psychosis were excluded.

The study was approved by the research ethics committee of Panzhihua University in Feb, 2013(reference number: 2013026). Written informed consent was obtained from all study participants. More than 20 voluntary individuals who can speak local dialect received training by the study investigators on communication and interviewing skills before the data collection. They were divided into six groups and all interview groups have been provided a professional physician. At the same time, we paid a return visit by random sampling to monitor the volunteers [13]. Interviewers visited the study community for data collection over 1 month between July 15 and August 15, 2013.

There were about 2300 families and 7700 people in this community. Systematic sampling by house doorplate number in three was conducted, and 730 families were selected. For the majority of families, there are three or more family members. Only one eligible resident in each family was recruited, usually a household host if available. We have chosen to recruit the first host we met for each family. If all family members were absent for one month or refused to be interviewed, the family with the next doorplate number would be selected as a replacement. If families with 2 or 3 consecutive doorplate numbers, all did not respond, the next ten doorplate numbers would be considered for recruitment. A total of 26 families refused to be interviewed, 20 families were not reachable within 1 month and 11 people that were unavailable because of mental problem. The final study cohort included 684 participants from Beichuan County who were representative of survivors in the heavily hit area.

All participants were interviewed using a structured interview questionnaire to obtain data on socio-demographic characteristics (age, gender, marital status, education, occupation) and earthquake related losses (property damage, personal injury, family member death). Posttraumatic stress symptoms were assessed using the subscale of PTSD Checklist-Civilian Version (PCL-C), which is the internationally recognized screen tool for PTSD with high reliability and validity [14,15]. The instrument is a self-reported 17-item symptom scale that corresponds to DSM-IV criteria [15]. The diagnosis of PTSD was determined by a clinical psychologist using the Chinese version of PCL-C [14,16,17] with Cronbach alpha coefficient of 0.82 and split-half reliability of 0.65 [16].

The 17 items of PCL-C each is with a score from 1 to 5: 1 = not at all; 2 = a little; 3 = quite a bit; 4 = extremely; 5 = very extremely. The maximal total score for 17 items is 85. Participant with a score of 50 or greater was classified as having probable PTSD. With PCL-C score of 50 as the diagnostic cut-off, the sensitivity was approximately 80% [18]. This cut-off point was used in the present study to identify PTSD cases.

According to the 4th edition of Diagnostic and Statistical Manual of Mental Disorder (DSM-IV) proposed by the Harvard Refugee Trauma Group [19], PTSD includes three groups of symptoms: B (intrusive re-experiencing, 5 items), C (avoidance or numbness, 7 items) and D (hyper-arousal, 5 items). Symptoms B positive group requires at least one of the five intrusive re-experiencing items to get a score of over 3. Symptoms C positive group requires at least three of the seven avoidance and numbness items to get a score of over 3. Symptoms D positive group requires at least two of the five hyper-arousal items to get a score of over 3 [19]. Cronbach’s alpha coefficient is 0.84. In this study, we did not use DSSM-IV criteria but used PCL-C score of 50 as the diagnostic cut-off. We compared the frequency of different PTSD symptoms (B, C, D) among all subjects as well as probable PTSD sufferers.

All data were analyzed by statistical software SPSS 17.0 (SPSS, Chicago, Illinois, USA). Descriptive statistics were computed for demographic characteristic variables. Chi-square test was used to examine differences in categorical variables between those who were suffered from PTSD and those who were not. Multivariate logistic regression was used to assess the risk factors of PTSD.