Tourette syndrome is a neurological disorder that develops in childhood or adolescence in which patients have involuntary tics involving sudden movements or vocalizations that are rapidly repeated. The symptoms usually occur several times a day, every day or intermittently and are usually mild, but can be severe.
The condition is believed be to associated with many genetic and environmental factors, Dr. Carol A. Mathews and her associates note. While few studies have examined the role of environmental factors, there are suggestions that incidents before or just after birth, as well as the mother's prenatal habits, effect the development of the disorder, its severity, and the risk of having another neurologic condition.
Mathews, from the University of California in San Francisco, and her team hypothesized that reductions in oxygen in the womb, a known effect of smoking, could increase the risk of developing Tourette's syndrome in those with a genetic susceptibility.
To test this theory, the research team evaluated members of three groups of people with the syndrome, which included 53 individuals from Costa Rica, 99 individuals of Ashkenazi Jewish descent, and 28 who had a sibling with the syndrome. The subjects' ages ranged from 3 to 59 years, but 60 percent were younger than 14 when they were interviewed.
The investigators report in the American Journal of Psychiatry that the average tic severity score was 38.6 out of a possible 50.
The presence of obsessive-compulsive disorder and self-injurious behavior was strongly associated with tic severity. Attention deficit/hyperactivity disorder was also associated with tics, but the association was not as strong as were the other two disorders.
More than half of the subjects reported at least one adverse event that occurred before or shortly after birth, but these were generally similar to that in the general population. Parental factors also did not seem to affect risk.
However, after accounting for the effect of patient group, gender and family history, maternal smoking was significantly associated with total tick and vocal tic severity. In fact, statistical calculations showed that maternal smoking accounted for 42 percent of the variance in tic severity.
Maternal smoking was also associated with an eight-fold increased risk of obsessive-compulsive disorder.
The researchers suggest that the association between smoking and tic severity and obsessive-compulsive disorder is evidence that chronic oxygen deprivation during fetal development increases the risk. However, they cannot rule out the possibility that maternal smoking is an indicator of another factor associated with the syndrome that has yet to be uncovered, such as socioeconomic status or attention deficit/hyperactivity disorder in one or both of the parents.