Research published in the Journal of Epidemiology and Community Health casts doubt on the belief that organophosphate poisoning causes symptoms of depression among Gulf War veterans and farmers, who are exposed regularly to these chemicals.

Several studies have found that people who are regularly exposed to organophosphates are more likely than the general population to have symptoms of depression, including irritability, difficulty concentrating and poor sleep patterns.

But these studies do not prove that organophosphates are responsible for these symptoms.

Because an individual's genetic make-up (genotype) is randomly determined from their parents' genotype at the time of conception, genes can be used to test whether a non-genetic factor (for example, organophosphates) causes a disease.

The PON1 Q192R gene comes in three versions (QQ, QR or RR) and individuals with the RR version tend to metabolise organophosphates more slowly than those with either of the other versions.

Several previous studies have shown that Gulf War Veterans and sheep dippers with the RR genotype had a higher probability of symptoms.

In a bid to look at the association more closely, the authors tested out the theory among older women between the ages of 60 and 79, who would not have been habitually exposed to organophosphates in the course of their employment.

The women were already part of a long term study of women's health, involving more than 4,000 participants from 23 British towns.

They were surveyed about their levels of depression, and blood samples were taken for genetic testing.

Women with the genetic variant were significantly more likely to report depression than those without, the findings showed.

These new findings suggest that the association of this gene with depressive symptoms is unlikely to be explained by organophosphate poisoning, because the association is the same, irre
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Contact: Emma Dickinson
edickinson@bmj.com
44-020-738-36529
BMJ Specialty Journals
20-Dec-2006