By Eleanor McDermid, Senior medwireNews Reporter
A case–control study suggests that people have an increased risk for developing bipolar disorder if their mothers smoked during pregnancy.
“Given that smoking during pregnancy is potentially preventable by a number of measures, including antismoking campaigns and greater attention to smoking behaviors during obstetric visits, the findings could have clinical importance,” say lead researcher Ardesheer Talati (Columbia University, New York, USA) and team.
“However, if maternal smoking is simply serving as a proxy for deeper behavioral or genetic disturbances related to addictive behaviors that influence bipolar disorder, cessation per se may not have preventive effects.”
The team found that having a mother who smoked during pregnancy was associated with a significant 2.01-fold increased odds for being a case – one of the 79 patients with bipolar disorder – rather than one of the 654 controls, who were matched to the cases for variables including age and gender. The association was independent of variables such as birthweight, maternal alcohol use during pregnancy, and maternal lifetime psychopathology (ascertained from medical records).
The relationship with maternal smoking appeared strongest for bipolar disorder without psychotic features, which affected 46 patients. Having a mother who smoked during pregnancy was associated with a significant 2.28-fold increased odds for this subtype, whereas there was a nonsignificant 1.75-fold risk increase for bipolar disorder with psychotic features, which affected 33 patients.
In an editorial accompanying the study in The American Journal of Psychiatry, Mario Maj (University of Naples, Italy) agrees that the observed relationship could be explained by confounding. “The decision not to quit smoking during pregnancy may be related to antisocial traits, risk-seeking behavior, or a reduced attention to one’s own and the child’s well-being,” he says. “These traits may reflect a familial vulnerability to bipolar disorder, which is transmitted to the offspring.”
But even if confounded, Maj believes that maternal smoking could still be one of the environmental factors contributing to bipolar risk in offspring. “Of note, it would be one of the most easily modifiable of those risk factors,” he says.
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