Section 12: Psychiatric Diseases

Conclusions

In general, the data that are available suggest that individuals with a psychiatric illness are at increased risk for crashes. Individuals with personality disorders (untreated or treated), untreated psychotics and psychoneurotics, untreated alcoholics, and individuals with schizophrenia appear to be at-risk. However, as noted above, there are a number of methodological weaknesses that limit the findings. For example, the use of self-report data or data obtained from medical records and/or police reports are likely to result in an underestimation of crashes. In addition, the use of different diagnostic categories across studies makes comparisons difficult. Sample sizes per diagnostic category often are small. Importantly, few studies failed to consider amount of driving exposure. It is not unreasonable to expect that individuals with a psychiatric disorder drive substantially less than age- and sex-matched controls in the general population. Thus, available estimates of crash risk are likely to be underestimations.

An important consideration when examining the crash rates of psychiatric patients is the role of suicidal motivation. A number of studies have examined this relationship with some studies reporting higher crashes rates for psychiatric patients with suicidal ideation and suicide attempts (Cushman et al., 1990; Elkema et al., 1970; Selzer and Payne, 1962). However, others suggest that suicide plays a limited role in motor vehicle crashes (Isherwood, Adam, and Hornblow, 1982; Schmidt, Shaffer, and Zlotowitz, 1977). It is important to note that the majority of studies in this area were completed before 1983, which may limit the findings. Even with that limitation, it may be that single-vehicle crashes involving drivers with psychiatric disorders could be used as a red flag for suicidal ideation in this population.

Future Research Considerations

A number of variables need to be considered in future research including: 1) diagnosis and criteria used to establish a diagnosis, 2) duration and severity of illness, 3) prescription medications-type of medication and compliance, and 4) amount of driving exposure. A major limitation in the existing literature is the lack of uniformity in diagnostic criteria across studies. Use of standardized diagnostic criteria (e.g., DSM-IV) in future studies would help to alleviate this limitation. In addition, comparison between the earlier and later studies is difficult because of methodological differences including differences in duration and severity of illness,use of control groups, and adjustments for driving exposure. The effects of psychotropic drugs (e.g., anti-psychotics, antidepressants, benzodiazepines, etc.) on driving performance are an important consideration when assessing crash risk. Unfortunately, there are few epidemiological field studies investigating this relationship, and those that are available have methodological limitations. Those studies that are available are examined in Section 13 (Drugs) of this review. In future studies, the inclusion of data on psychotropic drug use and the use of statistical control for drug use would be beneficial in advancing our knowledge of the effects of psychotropics on crash risk.

Table 33  Guidelines for Psychiatric Diseases

ADD = Attention Deficit Disorder
ADHD = Attention Deficit Hyperactivity Disorder
DLA = Driver Licensing Authority