Women with perinatal depression appear to have altered circadian rhythms. Using light to reset the body clock may improve symptoms.
Our bodies run on internal clocks that, in concert with light, wake us up in the morning and leave us sleepy by night time. This circadian rhythm is partly regulated by a suite of genes. These control not only the sleep-wake cycle but also a host of other functions, including metabolism, hormone secretions and body temperature – all of which cycle throughout the day.
Something seems to go awry in depression. People with severe depression tend to experience disruptions to their circadian rhythms. Depression can give people daytime sleepiness and night-time insomnia, and in people with the condition.
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Perinatal depression – which occurs during and after pregnancy – seems to be similar. Women tend to get less sleep when they are pregnant, particularly if they have perinatal depression.
To find out if circadian genes might play a role, Massimiliano Buoli, Cecilia Maria Esposito and their colleagues at the University of Milan, Italy, looked at seven such genes in 44 women in the third trimester of pregnancy. Thirty of the women had been diagnosed with perinatal depression.
Clocking on and off
By looking at whether epigenetic tags called methyl groups were attached to the genes, the researchers could tell how active these genes were. They found that three circadian genes were more active and one circadian gene was less active in the women who had been diagnosed with depression than those who didn’t have the condition.
The team also found that the more methyl groups there were, the more severe a woman’s symptoms were likely to be. This suggests that the greater the difference in circadian gene activity, the more likely a woman is to experience symptoms of depression, say Buoli and Esposito, who presented the findings at the annual meeting of the European College of Neuropsychopharmacology in Copenhagen, Denmark, last week.
There are likely to be plenty of other genes that also play a role, says Amy Ferguson at the University of Glasgow, UK. “There are so many genes involved, and we’re still finding out what all of them do,” she says.
Light treatment
“The work is tremendously exciting,” says Katherine Sharkey at Brown University in Rhode Island. “It is molecular evidence that behavioural disruptions associated with perinatal depression are manifesting in genes that we know are central to controlling the biological clock.”
Sharkey has found that using a lightbox that mimics natural daylight may improve the symptoms of perinatal depression. , she found that those given a lightbox and sleep routine alongside routine treatment saw their symptoms improve. “Everybody got better, but the women given a circadian intervention did better [than those without],” says Sharkey, who has not yet published the results.
Sharkey doesn’t yet have enough evidence to recommend the treatment more widely, but there is plenty of evidence that suggests a good sleep routine and daily outdoor exposure to sunlight is good for mental health. “In a typical office space the light level is 300 to 400 lux, but on a bright sunny day, outside can be 50,000 lux,” says Sharkey. “You can see your work and see what you’re doing, but your poor biological clock might not be sure if it’s morning or night.”
