Abstract
Objective:
To examine the association between late adolescence ADHD and the risk of serious injury in early adulthood.
Method:
A nationwide cohort study utilizing data from the Military Health Examinations Database for potential military recruits (age 16.5–18 years), cross-referenced with the Israeli National Trauma Registry (2008–2020). Individuals with and without ADHD (mild/severe) were compared for early adulthood injury risk using Cox models.
Results:
This study compared 76,403 participants with mild ADHD (18.76%) and 330,792 without (81.24%), alongside 2,835 severe ADHD participants (1.11%) versus 252,626 without (98.89%). Adjusted hazard ratios for injury-related hospitalization were 1.27 (95% CI [1.17, 1.37]) for mild ADHD and 1.40 (95% CI [1.09, 1.79]) for severe ADHD, compared to non-ADHD.
Conclusions:
Adolescents with ADHD, regardless of severity, had a significantly higher risk of hospitalization due to injury that persists into early adulthood, underscoring the importance of recognizing ADHD as an injury risk and incorporating it into injury prevention strategies.
Background
Attention-deficit hyperactivity disorder (ADHD) is a prevalent neurodevelopmental disorder that affects individuals across the lifespan, with an estimated global prevalence of around 5% to 10% in children and 2% to 5% in adults(Fayyad et al., 2017; Polanczyk et al., 2014). In the United States, it is estimated that between 8.8% and 11.0% of children aged 4 to 17 years are diagnosed with ADHD (Visser et al., 2014). In Israel, the estimated prevalence is even higher, amounting to 14.4% among children aged 5 to 17 years (Davidovitch et al., 2017). In contrast, the prevalence among adults is reported to be lower, with ADHD affecting approximately 4.3% of the adult population in the U.S. (London & Landes, 2021). This difference is thought to result, at least partly, from under-diagnosis in the adult population, with the diagnostic tools being different from those used for children. In the last few decades, there has been a substantial increase in the diagnosis and treatment of ADHD in Israel, with the consumption of ADHD medications more than doubling between 2005 and 2012 (Ponizovsky et al., 2014).
In addition to difficulties in social, academic, or occupational functioning, one concern related to ADHD is the increased risk of injuries among individuals with this condition. In 2017, a total of 1,845 Israelis died due to trauma, accounting for 54.8% of deaths between ages 18 and 24 years and 26.1% between 24 and 45 years (Israeli Central Bureau of Statistics, 2019). Additional severe toll is taken in the form of injury and disability.
Several studies have examined the relationship between ADHD and injury risk, with evidence suggesting that individuals with ADHD are more prone to experiencing injuries compared to those without the disorder (Chang et al., 2014; Dalsgaard et al., 2015; Guy et al., 2016; Lindemann et al., 2017; Merrill et al., 2009; Shem-Tov et al., 2019; Sun et al., 2019). This association is well described in children and adolescents, including a meta-analysis (Ruiz-Goikoetxea et al., 2018).
The increased risk of injury translates to increased mortality, specifically unnatural mortality, in individuals with ADHD (Dalsgaard et al., 2015). The contribution of other psychiatric comorbidities to this increased mortality was also described (Sun et al., 2019). This phenomenon can be partially explained by the fact that individuals with ADHD are prone to risky behavior patterns (Shoham et al., 2021), particularly hazardous driving patterns (Bron et al., 2018). ADHD has also been proven to be a risk factor for anti-social behavior and substance abuse, and subsequently to criminal behavior, with staggeringly higher rates of arrests, convictions, and incarcerations (Mannuzza et al., 2008).
It is worth mentioning that, in the case of ADHD, providing appropriate treatment is considered effective in improving outcomes (Ruiz-Goikoetxea et al., 2018; Shaw et al., 2012). This underscores the value of considering and adopting relevant policy changes, as suggested by Ornoy and Spivak (2019), who calculated a possible Benefit to Cost ratio of up to 7.02 for screening and treating ADHD in Israeli primary school students.
Most previous studies focused on specific types of injuries and did not examine the overall injury risk and outcomes in individuals with ADHD. The age ranges, and effect size also varied across the studies, apart from the differences in study settings and methodologies. Most of these studies examine the pediatric population even though ADHD often continues to affect the adult’s life. Understanding the association between ADHD and injury is essential for developing targeted interventions to reduce the risk of injury in individuals with ADHD. In this study, two large nationwide databases were cross-referenced to create a large cohort of ADHD adolescents and controls, intending to examine:
1) The effect of ADHD in adolescence on the risk of hospitalization in early adulthood due to injury (any injury, by injury severity, and injury mechanism).
2) The effect of ADHD on injury-related in-hospital mortality and utilization of critical hospital resources (hospital length of stay, admission to intensive care unit and need for surgical intervention).
Methods
Study Design and Data Source
A historical cohort study was conducted based on cross-referencing the data from the Military Health Examinations Database (MHED) in the Israel Defense Forces (IDF), representing the exposure variable, with the data from the Israeli National Trauma Registry (INTR), representing the outcome variables, recorded between 2008 and 2020.
Medical fitness for duty is determined and logged for all potential recruits for military service (as defined in the Israel Security Service Law) and recorded as an ordinal measure termed the “Medical Profile” (Knesset – Israeli Parliament, 1986). All potential recruits undergo medical assessment and are assigned a profile during their initial assessment in the recruitment office, regardless of whether they are eventually recruited or exempt from service. The data are based on a self-reporting questionnaire, physical examination, urinalysis, and medical information provided by the potential recruit. Further examinations and referral to specialist assessment and outpatient testing are performed as necessary. Medical and psychiatric diagnoses are compiled into diagnostic codes, which are assigned a severity level. The diagnostic code with the highest degree of severity determines the final medical profile and dictates the potential recruit’s fitness for service, specifically for combat or combat-adjacent service.
The INTR is an extensive database of hospitalized trauma patients, providing broad geographic and demographic coverage in the country (Israel National Center for Trauma & Emergency Medicine Research, 2016). Most of the trauma centers in Israel participated in the INTR, including all six level I trauma centers, which cover more than 90% of all national trauma cases and 98% of the severe cases. The INTR includes all hospitalized trauma patients classified based on an International Classification of Diseases, Ninth Revision, Classification Modification (ICD-9-CM) diagnosis code of 800-959.9, including deaths in the Emergency Department (ED) and transfers. The INTR does not include patients who died at the scene of the event or on the way to the hospital, were discharged following treatment in the ED, or were admitted 72 hr or more following the injury. Injuries resulting from poisoning, drowning, or suffocation also are not included in the registry. In order to avoid duplicate entries for transferred patients, their most recent hospitalization data were used. Trained trauma registrars record data reported in the registry at each trauma center under the supervision of a trauma director and trauma coordinator. Electronic files are transferred to the INTR at the National Center for Trauma and Emergency Medicine Research, where extensive logical tests and quality assurance are carried out to ensure their reliability and completeness prior to data analysis. Unclear, erroneous, or missing data are referred back to the trauma centers for clarification or completion, leading to a missing data rate of less than 0.5% of entries.
This research received the approval of the Institutional Review Boards from the Sheba Medical Center (Number 5138-18-SMC) and the headquarters of IDF Chief Medical Officer (Number 2263-2021).
Inclusion and Exclusion Criteria
For assessment of the association of mild ADHD with the risk of injury, individuals who attended the recruitment office between 2015 (when the diagnostic code for mild ADHD was first introduced) and 2020 were included. For severe ADHD, individuals who attended the recruitment office between 2008 and 2020 were included. Individuals who were outside the usual age margins for reporting to the recruitment office (16.5–18 years) were excluded, as they represent special populations outside the scope of this study and shift the distribution of follow-up ages in the study. For quality assurance purposes, individuals for whom the age of birth in the MHED was not in accordance with the reported age and date of injury in the INTR, were excluded. This study conducted separate comparisons for severe ADHD and mild ADHD. Of note, individuals with severe ADHD, as defined in our study by their “military medical profile,“ are exempt from combat duty assignment, whereas those with mild ADHD may be assigned any duty, depending on other co-existing medical conditions. To compare individuals with severe ADHD to controls with similar risk exposure regarding the nature of military service, individuals with severe ADHD were only compared to controls with similar medical profiles unfit for combat service. Mild ADHD does not affect the overall medical profile; thus, these individuals were compared to all other recruits.
Outcomes
The diagnostic code for attention-deficit hyperactivity disorder was an exposure variable, and this study’s primary outcome was the risk of overall traumatic injury resulting in hospitalization. Only injuries that occurred later than the report to the recruitment office were sought when cross-referencing the databases. The study participants were followed whether admitted to a hospital or not due to injury in one of the hospitals included in the INTR during 2008 to 2020. Severe and critical injury (Injury Severity Score [ISS] 16-75), injury mechanism, mortality, and utilization of hospital resources (hospital length of stay [LOS], admission to intensive care unit [ICU] and need for surgical intervention) were the secondary outcomes.
The data measured included age, gender, socioeconomic status (SES), ADHD, neuropsychiatric comorbidities, hospital admission due to injury, injury mechanism, injury severity score (ISS), utilization of critical hospital resources and disposition at hospital discharge (in-hospital mortality, referred for rehabilitation service). Age in years was compared as mean (standard deviation) and median (interquartile range). Socioeconomic status, determined by the place of living, was categorized as low (lower 30%), middle (30%–70%) and high (highest 30%) (Central Bureau of Statistics, 2019). Mechanism of injury was classified into motor vehicle collision (MVC), fall, burn/fire, other unintentional (which included unintentional struck from object/person, cuts/piercing, injury from a machine, unintentional firearm injuries and others), intentional and unidentified mechanism. Injury severity score was grouped into four categories (1–8, 9–14, 16–24, and 25–75) (Rozenfeld et al., 2014), which were then grouped into two categories (1–14 and 16–75) in the model estimating the risk of severe and critical injury (ISS 16-75). Relevant comorbidities (substance abuse disorder and impulse control disorders) were obtained from the MHED based on their diagnostic codes.
Statistical Analysis
Data analysis was performed using R version 4.3.1 (R Core Team, Vienna, Austria). Descriptive data were compared using Chi-square test or Fisher’s exact test as appropriate for categorical variables, Student’s t-test or Man-Whitney test for continuous variables with and without normal distribution, respectively. The incidence rates for hospitalization due to any injury, specific injury mechanisms and severe injury (ISS 16-75) were calculated as cumulative number of events divided by cumulative person-years. Kaplan-Meir analysis was performed to assess the cumulative incidence of injuries leading to hospitalization as a function of ADHD diagnosis.
Cox Proportional Hazards Regression models were performed to estimate the influence of ADHD on the risk of any injury and the risk of specific injury mechanisms and severe and critical injury (ISS16-75) while controlling for possible confounding factors. Interactions and multi-collinearity between the independent variables were tested using variance inflation factor (VIF) for their influence on the dependent variables.
Descriptive data values were reported as percentages for the categorical variables, as mean (standard deviation) and median (interquartile range) for the continuous variables. Incidence rates were displayed as cases per 100,000 person-years with the corresponding 95% confidence intervals (CI). Results from the Cox Proportional Hazards models were presented as hazard ratios (HR), with the corresponding 95% CI. A p-value < .05 was considered statistically significant.
The manuscript was composed in accordance with the Strengthening the reporting of observational studies in epidemiology (STROBE) statement (von Elm et al., 2007).
Results
A flow chart showing the study exclusion process is displayed in Figure 1. Seventy-six thousand four hundred three individuals with mild ADHD were compared with 330,792 individuals without ADHD in the years 2015 to 2020, and 2,835 individuals with severe ADHD were compared with 252,626 individuals without severe ADHD in the years 2008 to 2020. Their baseline characteristics are detailed in Table 1. When comparing individuals with mild or severe ADHD to their respective control groups, significant differences were observed in terms of gender, age (mean and median), and SES (Table 1).

Flow diagram of the study’s process inclusion, exclusion and division to comparison groups for (A) mild ADHD and (B) severe ADHD.
Baseline Characteristics for Adolescents and Young Adults With ADHD Compared With a Cohort Without ADHD.
Note. IQR = interquartile range; % = percentage; SES = socioeconomic status; ADHD = attention deficit/hyperactivity disorder; NS = non-significant (p-value ≥ .05).
It is important to note that mild ADHD and severe ADHD are exclusive diagnoses, and as a result, their effects were evaluated independently from the N1 and N2 populations, respectively.
In the mild ADHD group, the incidence rate of injury-related hospitalization was 182.0 (95% CI [169.8, 194.8]) per 100,000 Person Years (PY) compared to 140.8 (95% CI [135.6, 146.1]) per 100,000 in the non-ADHD group (17.5 (95% CI [13.9, 21.7]) and 13.8 (95% CI [12.2, 15.5]), respectively for severe injuries (ISS ≥ 16)), while in the severe ADHD group, the incidence rate was 167.5 (95% CI [129.0, 213.8]) per 100,000 PY compared to 107.6 (95% CI [104.2, 111.1]) per 100,000 PY (10.3 (95% CI [2.8, 26.4]) and 11.5 (95% CI [10.4, 12.7])), respectively for severe injuries), see Table 2.
Incidence Rates and Cox Proportional Hazard Ratios for Overall Injury, Severe and Critical Injury (ISS16+) and Specific Injury Mechanisms Among Adolescents and Young Adults With and Without ADHD. d
Note. ADHD = attention deficit/hyperactivity disorder; ISS = injury severity score; n = number of hospitalized cases for injury; MVC = motor vehicle collision; HR = hazard ratio; CI = confidence interval; Ref. = reference group.
The mild ADHD cohort constituted 76,403 participants (18.76%) and the group without ADHD constituted 330,792 participants (81.24%) for each analysis. In contrast, the severe ADHD group composed 2,835 participants (1.11%) and was compared with 252,626 individuals without ADHD (98.89%).
Unintentional other included unintentional struck from object/person, cuts/piercing, injury from machine and others.
Adjusted for gender and socioeconomic status (classified into low, middle and high), impulse control disorder, and substance abuse disorder.
It is important to note that mild ADHD and severe ADHD are exclusive diagnoses, and as a result, their effects were evaluated independently from different populations, N1 = 407,195 and N2 = 255,461, respectively.
The incidence rates are significantly different between the comparison groups.
p < .001. **p < .01. ***p < .05.
In the Cox proportional hazard regression, adjustments were made for gender, socio-economic status and comorbidity with impulse control or substance abuse disorders. Multi-collinearity was ruled out by VIF calculation (1.00). Both mild (unadjusted HR: 1.29, 95% CI [1.20, 1.40]; adjusted HR: 1.27, 95% CI [1.17, 1.37]) and severe (unadjusted HR: 1.55, 95% CI [1.21, 1.99]; adjusted HR: 1.39, 95% CI [1.09, 1.78]) ADHD were associated with an increased risk for injury-related hospitalization (Table 2). This association became less apparent and was non-significant when examining the risk for more severe injuries (ISS16-75): Unadjusted HR = 1.27 (95% CI [0.99, 1.62]); adjusted HR = 1.24 (95% CI [0.97, 1.60]) for mild ADHD and unadjusted HR = 0.90 (95% CI [0.34, 2.40]); adjusted HR = 0.76 (95% CI [0.28, 2.04]) for severe ADHD (Table 2). This is most likely due to the decreased overall incidence of these injuries.
Table 2 also displays the incidence rates and the results of the Cox proportional hazard model for specific injury mechanisms. It was only performed for the mild ADHD population due to the small overall number of injuries in the severe ADHD group. A statistically significant association was found between mild ADHD, motor vehicle collisions, and other unintentional injuries.
Figure 2 displays the Kaplan-Meyer curves of cumulative injury-related hospitalizations of individuals with mild and severe ADHD compared to the relevant control groups.

Kaplan-Meyer curves showing the cumulative risk of injury for individuals with (A) mild and (B) severe ADHD comparing to their respective controls.
Amongst the participants hospitalized due to injuries, no significant differences were found concerning mortality, intensive care unit admission, need for surgery, length of stay, and need for rehabilitation. These results are displayed in Table 3.
In-Hospital Mortality and Hospital Resource Use Characteristics Among Adolescents and Young Adults Hospitalized for Injury by ADHD.
Note. ADHD = attention deficit/hyperactivity disorder; NS = non-significant (p-value ≥ .05).
It is important to note that mild ADHD and severe ADHD are exclusive diagnoses, and as a result, their effects were evaluated independently from the N1 and N2 populations, respectively.
Discussion
The findings of this study indicate that a diagnosis of ADHD among young adults, regardless of its severity, is associated with an increased risk of injury that requires hospital admission.
This finding is consistent with the results of previous studies that have also suggested an association between ADHD and an increased risk of injury, including the magnitude of the effect. A systematic review and meta-analysis conducted by Ruiz-Goikoetxea et al. (2018) showed an association between ADHD and increased risk of injuries in children and adolescents, with pooled odds ratios ranging between 1.39 and 1.53. Chang et al. (2014) have demonstrated a similar association in adolescents and young adults with ADHD, specifically with injury-associated hospitalization following transport accidents, with hazard ratios of 1.45 to 1.47. Another study by Shem-Tov et al. (2019), following a cohort of children and adolescents, found a hazard ratio of 1.63. This consistency across multiple studies strengthens the evidence supporting this association.
The population of this study is unique as the majority of this cohort was recruited for military service for 2 to 3 years within the follow-up period. Since a diagnosis of severe ADHD precludes the participants from combat service, severe ADHD may have a protective effect due to decreased risk exposure. To prevent that bias, we compared participants with severe ADHD to controls with similar medical profiles which have similar limitations to their service assignments.
While not statistically significant, there was a borderline tendency toward a higher likelihood of severe and critical injuries (ISS16-75) in individuals with mild ADHD. However, no significant association was observed between severe ADHD and the risk of severe and critical injuries. This difference is most likely related to fewer injury events among individuals with severe ADHD. Additionally, it may be related to the exemption from combat service granted to individuals with severe ADHD.
ADHD is known to be associated with substance abuse (Dalsgaard et al., 2014) and impulse control disorders (Barkley & Brown, 2008), which in turn may lead to an increased risk of injury. This study demonstrates the increased risk of injury associated with ADHD, even when adjusting to these comorbidities. The association of ADHD with an increased risk of injury was demonstrated both for intentional and unintentional injuries. This is particularly important as it may guide potential preventive interventions. Injury outcomes were similar between trauma casualties with and without ADHD, as well as hospital resources utilization, which assists in quantifying the burden associated with the excess injuries associated with ADHD and can aid with future cost analyses.
Given that the injury data were ascertained from a nationwide registry and considering that there are no military hospitals in Israel, it is pertinent to note that hospitalization records encompass injuries incurred both during and outside of military service. Hence, it is plausible that a portion of the injuries occurred among subjects during their military tenure and as part of their military duties. However, our dataset does not include explicit information on whether injuries occurred during military service. Given the variable nature of military service duration, coupled with reserve service following discharge, reliably estimating the proportion of injuries during military service becomes challenging. To address the potential contribution of injuries occurring during military service, we conducted an additional analysis examining the interaction between medical profiles fit for combat service and mild ADHD, revealing no significant interaction between the two.
Due to variations in elligibilty for combat duty and the delayed introduction of a diagnostic code for mild ADHD to IDF medical guidelines, this study did not directly compare the risk of injury between individuals with mild and severe ADHD. Nonetheless, it is plausible that individuals with mild ADHD may be more prone to injuries than those with severe ADHD. This potential difference could be attributed to the tendency of individuals with mild ADHD to underestimate their condition, leading to lower medication adherence and increased vulnerability to injuries, given the effectiveness of proper treatment in improving outcomes (Ruiz-Goikoetxea et al., 2018; Shaw et al., 2012). An even more important factor might be their increased risk exposure due to possible enlistment for combat duty, which introduces additional risks such as combat injuries, firearm and machinery accidents, etc. This is reflected by the association between a fit for combat service medical profile and the increased risk for trauma-related hospitalization in the multivariable model.
This study has several limitations. First, the retrospective nature of the study prevents any conclusions regarding causality. However, in this cohort, the diagnosis preceded the injury in all cases by design. Second, the nature of the INTR database rules out trauma casualties who died before arriving at the hospital, which may lead to underestimating the effect. In addition, this study did not include minor injuries that did not arrive or were discharged from the emergency department. Third, no documentation regarding medical treatment was available in the database. Instead, the diagnostic code assigned represents the severity of symptoms and functional level, with or without medical therapy. Fourth, while data regarding injury types and circumstances are available, the small numbers in the subgroups limit the ability to draw conclusions regarding differences in injury patterns associated with ADHD. Fifth, due to the late introduction of a diagnostic code for mild ADHD, follow-up time for these individuals was significantly shorter. However, the abundance of this diagnosis allowed for a clear demonstration of association. Lastly, this study was conducted entirely in Israel, and includes some specific features (e.g., mandatory military service) that may affect its generalizability.
In conclusion, this study demonstrates that diagnosis of ADHD, both mild and severe, in late adolescence is associated with an increased risk for serious injury in early adulthood. This supports the need for developing preventive strategies aimed for this population, through early detection, treatment, education and more. Larger cohorts may allow for better characterization of injury circumstances and patterns.
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by THE ISRAEL SCIENCE FOUNDATION (Grant No. 2808/21).
Author Biographies
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