Associations Between Adverse Underwater Events and ADHD Diagnosis Among Military Divers

Introduction

Adult ADHD (A-ADHD) is a condition characterized by a persistent pattern of inattention and/or hyperactivity-impulsivity that demonstrably interfere with social, academic, and/or occupational functioning (American Psychiatric Association [APA], 2013). A-ADHD is associated with significant functional impairment (Kessler, Lane, Stang, & Van Brunt, 2009), with inattentive symptoms more common in adults than symptoms of hyperactivity or impulsivity (Asherson, 2005; Biederman, Mick, & Faraone, 2000). A-ADHD also has significant impact on work (Adamou et al., 2013; Biederman et al., 2006; de Graaf et al., 2008) and has been associated with an increased risk of accidents and workplace injuries, particularly traffic accidents (Chang, Lichtenstein, D’Onofrio, Sjölander, & Larsson, 2014; Küpper et al., 2012) and unsafe driving behaviors (Knouse, Bagwell, Barkley, & Murphy, 2005). Other studies found a 2.0 relative odds of workplace accident injuries (Kessler et al., 2009).

The prevalence of A-ADHD in the workplace has been estimated from 2.9% (Biederman, 2005) to 4.4% (Kessler et al., 2005; Kessler et al., 2006). Available epidemiology reports are based on Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; APA, 1994) criteria, and mainly used samples from the United States.

As far as could be ascertained, no studies documenting prevalence of A-ADHD among professional divers are available. However, given the prevalence of A-ADHD in the working population, it can be assumed that such individuals may also be working in the field of professional diving.

A-ADHD and diving is a topic of debate, as reference to ADHD generally elicits a number of concerns in the context of hyperbaric medicine, and many afflicted individuals may be considered unfit to dive (Sawatzky, 2010). Although many individuals with A-ADHD may safely be diving, the condition has major potential occupational health and safety implications, as accidents underwater may have severe consequences for afflicted individuals and team members. Considerations when determining psychological competency to dive may include the severity of symptoms and its effect on safety performance (e.g., through challenges to self-regulation), and known risks for accidents and injuries. Furthermore, medical management of A-ADHD raises concerns regarding safety of medications under hyperbaric conditions, further raising the risk profile. Hyperbaric conditions encountered during diving are associated with central nervous system (CNS) suppression, which may render stimulant medication less effective. Furthermore, the use of stimulants may pose an increased risk for oxygen convulsion when a diver is exposure to elevated partial pressures of oxygen, while drugs that cause sedation may have an increased effect under hyperbaric conditions (Sawatzky, 2010).

Although there is no published evidence of problematic safety-critical behavior associated with A-ADHD among professional divers (e.g., no reports associating divers with A-ADHD and underwater accidents), there have been anecdotal reports of increases in the number of professional divers who are also diagnosed with A-ADHD, found on the Internet and also suggested by medical professionals in the field. This report briefly describes an analysis of adverse events recorded for navy divers, and their A-ADHD status.

Method

This analysis used retrospective records from 156 (11 female) South African Navy divers, to investigate any association of adverse underwater events (“accidents”) with A-ADHD diagnosis. Institutional review board (IRB) approval was obtained for this study. Divers were included if they dived regularly (as opposed to mainly supervising diving activities). All divers met the rigorous naval diving health standards. Navy divers typically prefer physical and practical activities, are by nature adventurous and risk-takers, and generally display low trait anxiety (Van Wijk, 2018).

Diagnosis of A-ADHD was determined through a clinical assessment, using Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; APA, 2013) criteria, by a clinical psychologist, and was conducted in the year preceding the data analysis. This sample of navy divers had an A-ADHD prevalence rate of 2.6% (four cases). Three cases were considered mild A-ADHD; the severity of the fourth was not known. The divers had an average of 3 years of operational diving experience, and adverse events from the previous 3 years were collected from their logbooks. A total of 24 cases (with one incident each; none fatal) were identified for the total group. Due to the nature of the data (see Table 1), an odds ratio (OR; with Fisher’s exact p) was computed using Stata 10.0.

OPEN IN VIEWER

Table 1.

Distribution of Cases.

		Cases of adverse underwater events
		Yes	No
Diagnosis of A-ADHD	Yes	1	3
	No	23	129

Results and Discussion

An OR = 1.87 indicated a difference in this sample. However, due to small numbers, it is difficult to extrapolate the findings to a larger population. The 95% confidence interval (CI) was [0.034, 24.353] (p = .491), but the lack of statistical significance should be interpreted with caution, as the low numbers would not provide the statistical power to detect significant differences unless extreme differences exist. It is thus unclear whether the increased risk observed in the sample can be extrapolated to a larger population of divers.

In further consideration of the results, a number of other factors could also have contributed to this outcome. First, military divers undergo stringent medical screening on entry, and it is possible that individuals with more severe forms of A-ADHD may have been excluded from entry into the field. The cases in this sample appear to represent milder forms of A-ADHD, who may have lower risk profiles. Second, navy divers adhere to very strict diving protocols to enhance safety, and underwater activity is closely controlled by supervisors, which may have assisted any at-risk divers to remain safe.

Due to the nature of the data, the analysis has a number of limitations. It did not consider any possible workplace accidents or incidents out of the water, nor did it account for the number of dives recorded per diver for the study period (some divers may have completed more dives than others).

In conclusion, there is not yet statistical evidence that mild A-ADHD places navy divers at significantly greater risk for adverse underwater events. The screening for severe forms of A-ADHD during initial medical assessment is recommended (Laukkala et al., 2017), as is further research to determine whether divers with A-ADHD is at greater risk for adverse underwater events.