The risk of motor vehicle injuries caused hospitalization and the risk of mental health illness: A nationwide, matched-cohort, population-based study in Taiwan

Abstract Background: Although motor vehicle injuries are a prevalent concern worldwide, research and clinical care have predominantly emphasized physical trauma, with comparatively less focus on the psychological impact experienced by survivors. Aims: To investigate the risk of the development of mental health issues after MVI. Methods and procedures: We included 39870 people with hospitalization due to MVI from January 1, 2000 to December 31, 2015, and 1076911 sex-, age- and index day-matched controls with hospitalization due to non MVI subset of the National Health Insurance Research Database in Taiwan. The Cox proportional hazard models were used to analyze the associations between the relevant demographics, and the psychiatric comorbidities and the risk of injury. Outcomes and results: The patients with hospitalization due to MVI had a 220% increased risk of overall mental health issues than the controls after considering all the confounding factors. What this paper adds? This nationwide, matched-cohort, population-based study in Taiwan showed that people with hospitalization due to motor vehicle injuries(MVI) are associated with increased risk of overall mental health issues. Introduction Motor vehicle injuries are a major public health concern worldwide, contributing significantly to morbidity, mortality, and healthcare burden including traumatic brain injuries, spinal cord injuries, fractures, internal organ damage, and polytrauma.. These injuries result from collisions involving cars, motorcycles, trucks, or other motorized vehicles, and can affect drivers, passengers or pedestrians. According to the World Health Organization (WHO), road traffic accidents cause approximately 1.19 million deaths annually (as of 2023), making them one of the leading causes of death globally—particularly among individuals aged 5 to 29 years. Few studies have investigated the development of risk of mental health issues in these patients under hospitalization due to motor vehicle accidents, and the published studies were limited to traumatic brain injuries and spinal cord injuries. Therefore, we conducted this study to investigate the risk of developing mental health issues in patients under hospitalization due to motor vehicle accidents by using the National Health Insurance Database in Taiwan. Methods 2.1 Data source: In this study, we used outpatient and hospitalization data from the Longitudinal Health Insurance Database (LHID), a subset of the NHIRD, to investigate the association between hospitalization due to motor vehicle accidents and mental health issues over a 15-year period (2000–2015) in Taiwan. The National Health Insurance (NHI) Program was launched in Taiwan in 1995, and as of June 2009 it included contracts with 97% of all medical providers in Taiwan with approximately 23 million beneficiaries, or more than 99% of the entire population in Taiwan (Ho Chan, 2010). The National Health Insurance Research Database (NHIRD) uses the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes to record diagnoses (Chinese Hospital Association, 2000), and all diagnoses of mental health issues(including anxiety, depression, bipolar disorder, sleep disorders, acute stress disorder/post-traumatic stress disorder, substance use disorders, dementia, schizophrenia, personality disorders and behavioral disorders) are made by board-certified specialists such as psychiatrists or neurologists. The NHI Administration randomly reviews the records of 1 in 100 ambulatory care visits, and 1 in 20 in- patient claims, to verify the accuracy of the diagnoses (National Health Insurance Administration, 2013), and several studies have demonstrated the accuracy and validity of the diagnoses in the NHIRD (Cheng, Kao, Lin, Lee, & Lai, 2011; Chou, Lin, Lin, Sung, & Kao, 2013; Liang et al., 2011). 2.2 Study design and sampled participants 2.2.1 Study design: This study was of a retrospective matched-cohort design. 2.2.2 Sample: Patients suffered from motor vehicle injuries were selected from January 1 2000, to December 31, 2015, according to ICD-9-CM code E810.x0 - E819.x0, E810.x1 - E819.x1, E810.x2 - E819.x2, E810.x3 - E819.x3, E810.x6 - E819.x6, E810.x7 - E819.x7 and E810 - E819. Each enrolled patient was required to be admitted to hospital at least one day. The patients diagnosed with injuries before 2000 or the patient had a pre-existing mental health issues before the incident, and the patients with no follow-up data or who the gender is unspecified were excluded. A total of 19936512 patients were enrolled, including 47161 subjects with hospitalization due to MVI and 1889351 hospitalization prognosis-, age-, sex-, comorbidity-, urbanization-, season, monthly income-matched and hospital accreditation level controls in hospitalization due to non MVI with a propensity score (Figure 1). 2.2.3 Covariates: The covariates included hospitalization prognosis(survive or death), sex, age group (<5, 5–14,15–24, 25–44, 45–64, ≧65 years), monthly income (in New Taiwan Dollars [NTD]; < 18,000, 18,000–34,999, ≧35,000), season, comorbidities, urbanization level of residence (level 1–4), and hospital accreditation level. The population level of residence was defined according to the population and various indicators of the level of development. Level 1 was defined as a population > 1,250,000, and a specific designation as a political, economic, cultural and metropolitan development. Level 2 was defined as a population between 500,000 and 1249,999, and as playing an important role in the political system, economy, and culture. Population levels 3 and 4 were defined as a population between 149,999 and 499,999, and < 149,999, respectively (Chang et al., 2014). Hospital accreditation level was based on their size, facilities, staff qualifications, and services provided according to Taiwan Joint Commission on Hospital Accreditation’s result. 2.2.4 Comorbidities: Baseline comorbidities included catastrophic illness(based on Ministry of Health and Welfare), diabetes mellitus(ICD-9-CM code 250), hypertension(ICD-9-CM code 401-405), hyperlipidemia(ICD-9-CM code 272), myocardial Infarction(ICD-9-CM code 410 and 412), cardiovascular disease(ICD-9-CM code 480-489), chronic obstructive pulmonary disease(COPD; ICD-9-CM code 490-496), pneumonia(ICD-9-CM code 480-488 and 507), respiratory failure(ICD-9-CM code 518.8), kidney disease(ICD-9-CM code 580-589), and epilepsy(ICD-9-CM code 345 and 780.3) 2.2.5 Outcome measures: All of the study participants were followed from the index date until the occurrence of an diagnoses of mental health issues including anxiety(ICD-9-CM 300), depression(ICD-9-CM 296.2–296.3, 300.4 and 311), bipolar disorder(ICD-9-CM 296.0 and 296.4-296.8), sleep disorders(ICD-9-CM 307.4 and 780.5), acute stress disorder(ICD-9-CM 308)/post-traumatic stress disorder(ICD-9-CM 309.81), substance use disorders(ICD-9-CM 291, 292, 303.3, 303.9, 304 and 305), dementia(ICD-9-CM 290.0-290.4, 290.8, 290.9, and 331.0), schizophrenia(ICD-9-CM 295), personality disorders(ICD-9-CM 301) and behavioral disorders(ICD-9-CM 312) made by board-certified specialists such as psychiatrists or neurologists at outpatient department/emergency department for over 3 times or requiring hospitalization. 2.3 Data analysis All analyses were performed using IBM Statistical Product and Service Solutions (SPSS) for Windows, version 22.0 (IBM Corp., Armonk, NY). χ2 and t-tests were used to evaluate the distributions of categorical and continuous variables, respectively. The multivariate Cox proportional hazards regression analysis was used to determine the risk of injuries, and the results were presented as the hazard ratio (HR) with 95% confidence interval (CI). The differences in the risk of injuries between the study and control groups was estimated using the Kaplan-Meier method with the log-rank test. A 2-tailed p value < 0.05 was considered to indicate the statistical significance (Table 6, Table 7). 2.4 Ethics This study was conducted in accordance with the Code of Ethics of the World Medical Association (Declaration of Helsinki). In addition, the Institutional Review Board of the Tri-Service General Hospital approved this study and waived the need for individual written informed consent . Results 3.1 Sample characteristics Of the 47125 patients with hospitalization due to MVI, 27311 (57.95%) were male, 208 were at aged<5, 1186 were at aged 5–14, 9925 were at aged 15–24, 13042 were at aged 25–44, 14339 were at aged 45–64, 8425 were at aged ≧65 years, and the mean age was 43.94 ± 20.08 years. There were no significant differences between the patients and controls in hospitalization due to sex, different motor vehicle caused injuries, hospitalization prognosis, age distribution, sex, comorbidities as catastrophic illness, hypertension, COPD, kidney disease and epilepsy, urbanization level of residence covariates after the propensity-score matching (Table 1, Table 2). 3.2 Kaplan-Meier model for the cumulative risk of mental health issues The Kaplan-Meier analysis for the cumulative risk of mental health issues in those with hospitalization due to MVI or non-MVI with the log-rank test showed a significant difference over the 15-year follow-up period (p < 0.001) (Figure 2). 3.3 Comparisons of the prevalence of mental health issues At the end of follow-up, 6132 of the 47161 (%) suffered from mental health issues when compared to 12391 of the 1076911 (%) controls (p < 0.001). The patients tended to have a higher percentage in suffering mental health issues than controls in all groups as sex, age groups, monthly income, season, comorbidities, urbanization level of residence and hospital accreditation level and also significant difference was shown (p < 0.001) (Table 4, 5). 3.4 Hazard ratios analysis of developing mental health illness after hospitalization due to MVI In the Cox regression analysis, after adjusting for sex, ages, monthly income, season, comorbidities, urbanization level of residence and hospital accreditation level, the adjusted HR was 2.204 (95% CI: 1.663–2.785, p < 0.001), which was a 1.204% increase in the risk of developing mental health issues compared to the controls. In other words the adjusted HRs were significant for the risk of developing mental health illness after MVI cased hospitalization compared to the controls. (Table 3) With regards to the type of mental health illness, the patients had a higher risk of anxiety, depression, bipolar disorder, sleep disorders, acute stress disorder/post-traumatic stress disorder, substance use disorders, dementia, schizophrenia, personality disorders and behavioral disorders when compared to the controls. (Table 6) Discussion 4.1 Association between MVI caused hospitalization and the risk of mental health illness In this study, MVI caused hospitalization was associated with an increased risk of mental health illness of all types. The adjusted HR of having a mental health illness was 2.204 (95% CI: 1.663–2.785, p < 0.001). The Kaplan-Meier analysis also revealed a significant difference between the patients and controls over the 15-year follow-up period (p < 0.001). Among the different types of mental health illness, anxiety, depression, bipolar disorder, sleep disorders, acute stress disorder/post-traumatic stress disorder, substance use disorders, dementia, schizophrenia, personality disorders and behavioral disorders were associated with a higher risk. In addition, the patient with hospitalization due to MVI were at a higher risk of developing mental health illness when compared to the controls which were hospitalized due to non-MVI. 4.2 Association between relationship of MVI caused hospitalization and the risk of mental health illness: Previous research has shown that common psychological issues following traffic injuries include depression, anxiety/phobias, and post-traumatic stress symptoms (Bryant et al., 2010; Grant et al., 2008; Kenardy et al., 2018; O’Donnell et al., 2004). Reported rates of mental disorders after such injuries range from 30% to 50% in some studies (Bryant et al., 2010; Guest et al., 2018; Kenardy et al., 2018; Mayou & Bryant, 2001). When left untreated, these symptoms can progress into more severe psychiatric conditions such as major depressive disorder (MDD), post-traumatic stress disorder (PTSD), panic disorder, and generalized anxiety disorder (Grant et al., 2008; Kenardy et al., 2018). Additionally, individuals may develop behavioral problems including aggression or substance misuse (Beck & Coffey, 2007; Copanitsanou et al., 2018; deRoon-Cassini et al., 2010). Also, having an motor vehicle crash can associated with current major depressive episode, alcohol abuse among younger adolescents, and among older adolescents, was associated with alcohol abuse(Joah L Williams et al., 2015). Some studies also highlight that the total cost of illness—including both medical and rehabilitation expenses—can nearly double when psychological distress is taken into account (Chan et al., 2003). These findings underscore the critical need for early mental health screening and intervention following traffic-related injuries. 4.3 Possible mechanisms for the increased risk of mental health illness injuries in adults with hospitalization due to MVI: Several mechanisms may contribute to the heightened risk of mental health disorders in adults hospitalized due to motor vehicle injuries. First of all, the traumatic nature of the accident itself, often involving life-threatening situations, can trigger acute stress reactions that may develop into chronic conditions such as post-traumatic stress disorder (PTSD). Moreover, prolonged recovery of the physical injuries can lead to functional impairments, chronic pain, and loss of independence, all of which are strongly associated with depressive and anxiety disorders. Furthermore, hospitalization may disrupt social and occupational roles, contributing to feelings of helplessness, isolation, and financial stress. Biological responses to trauma, such as dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, may further exacerbate vulnerability to mental illness. 4.4 Limitation: Several limitations should be acknowledged in this study. First, the dataset lacked information on individuals’ prior psychiatric history and family history of mental illness, both of which are important risk factors that may confound the observed associations. Second, while the use of a national health insurance database provides a large sample size and comprehensive coverage, it is limited to administrative and diagnostic coding data. Therefore, the specific context and circumstances of the motor vehicle injury—such as whether it involved alcohol or drug use, fatigue, or other high-risk driving behaviors—could not be evaluated. Third, the generalizability of the findings is restricted to the Taiwanese population and healthcare system. Cultural attitudes, healthcare accessibility, and patterns of mental illness vary significantly across countries. In particular, the baseline incidence and recognition of psychiatric disorders differ worldwide, which limits the applicability of these findings to other populations. Additionally, the relatively short duration of follow-up may have prevented the detection of delayed-onset psychiatric disorders, such as chronic PTSD or major depressive disorder, that can emerge months or even years after injury. Therefore, long-term studies are warranted to capture the full scope of mental health consequences following motor vehicle trauma. Conclusion Our results show strong evidence to support the association between MVI caused hospitalization and the risk of mental health illness. Future studies with longer follow-up periods and the use of alternative research designs—such as prospective cohort studies or matched-control approaches—are needed to better clarify the temporal and potentially causal relationship between motor vehicle injury and the development of mental health disorders. References Williams, J. L., Rheingold, A. A., Knowlton, A. W., Saunders, B. E., & Kilpatrick, D. G. (2015). Associations between motor vehicle crashes and mental health problems: Data from the National Survey of Adolescents–Replication. Journal of Traumatic Stress, 28(4), 269–276. URL: https://doi.org/10.1002/jts.21983 Bryant, R. A., O'Donnell, M. L., Creamer, M., McFarlane, A. C., Clark, C. R., & Silove, D. (2010). The psychiatric sequelae of traumatic injury. The American Journal of Psychiatry, 167(3), 312–320. 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