Serotonin lower in shift workers

Workers who rotate between day and night shifts are at high risk for sleep and mood disorders. New research highlights a possible biological explanation—lower amounts of the key brain chemical serotonin.

Serotonin helps regulate the brain’s circadian cycle and also plays a large role in mood. Antidepressants such as fluoxetine (Prozac) and sertraline (Zoloft) increase production of serotonin that the brain’s nerve cells use to communicate.

Silvia Sookoian and her colleagues at the University of Buenos Aires in Argentina drew blood from 437 men who worked only the day shift at a local factory and 246 men who rotated shifts. The team found lower amounts of serotonin and a key serotonin breakdown product in the shift workers. While the difference in serotonin wasn’t dramatic, it was statistically significant, the researchers report in the Aug. 1 Sleep. They say that it might explain why some shift workers have difficulty adjusting to a rotating schedule.

In 2005, the drug company Cephalon of Frazer, Pa., received Food and Drug Administration approval to market modafinil (Provigil), a medication that works in an unknown way, for “shift work sleep disorder.” The company says that the condition is marked by excessive sleepiness, headaches, a lack of focus, and trouble sleeping after work. Cephalon claims that 25 percent of the 6 million people in the United States who regularly or occasionally work nights suffer from the disorder.