Magnetic field exposure may not have a directly causal relationship to suicide

Work-related suicide? Suicide at work? Work-induced suicide? The definitional issues tying work life to suicide, which by its nature has a multi causal pathway, are complex. These complexities, perhaps, explain why so little research has been conducted on the association between work factors and suicide.

Although the incidence of violent injuries in general has decreased dramatically since 1994, overall suicide rates have decreased only slightly from 1987 through 1997. Among men older than 19 years, suicides have decreased about 8% during this period. According to the Census of Fatal OccupationalInjuries (CFOI) conducted by the Bureau of Labor Statistics, the number of suicides identified as being work-related has been stable since1992.¹ However, the coding issues leading to classifying a suicide as work-related are problematic and inconsistent throughout the country, and the number of events that have a work-related component are probably underestimated. Of more than 1,500work-related suicides identified by CFOI, less than 1% were in the electric utility industry.

van Wijngaarden and colleagues find an increased risk for suicide among electric utility workers who have been exposed to magnetic fields. They offer a biologic pathway for this relationship, citing the effects of electromagnetic radiation on disturbances of melatonin regulation. Decreased melatonin production has been linked to depression, which in turn is a risk factor for suicide.

Magnetic field exposure is unlikely to be either a necessary or sufficient cause of depression or suicide, and its role relative to other predictive factors is likely to be small. However, certain persons may have increased vulnerability to this type of exposure, or interactive effects with other predictors of suicide may define particularly vulnerable times. This is a well-conducted study using available information, and the use of defined working cohorts is a rich source for etiologic research. However, the inability in this study to control for the main known predictors of suicide, such as drug use, mental illness, and family and social stresses, and especially the inability to measure depression and its onset severely limit the ability to define the role of electromagnetic exposure in the causal pathway of suicide.

The study found that the strongest risk for suicide was among the most recent exposures, suggesting either a relatively short latency period or a strong survival effect. Such a survival effect, in which those most vulnerable to exposure commit suicide early and those less vulnerable continue to accumulate exposure, is supported by the authors' theory that electromagnetic radiation has a stronger relationship with types of depression found among younger people. The relatively short latency—in contrast to the relation between depression and suicide, which is a complex path with a longlatency—suggests the possibility that magnetic fields operate as a prognostic factor rather than a risk factor to exacerbate the effects of existing depression or other risk factors for suicide, possibly leading to increased suicidal ideation. Most cases of depression do not lead to suicide, and other mental illnesses are much more predictive of suicidal behavior. If exposure to electromagnetic fields does increase the risk for depression or worsen depressive symptoms, treatment and prevention should focus on the depressive symptoms themselves.

What implications do these findings have for occupational medicine physicians? Although they certainly open the door for future research, the practical implication is that workers exposed to electromagnetic fields should be aware of the signs and symptoms of depression, and their physicians should ask about these symptoms during history taking and clinical examination.Primary care physicians should be aware of these symptoms in any of their working patients. Future research will hopefully elucidate the biologic pathway of this relationship, leading to more sophisticated prevention and treatment measures.