Out-of-Sync Biological Clock Could Be Linked to Depression

Our bodies are made up of clocks that keep time with the rotation of our planet — and when these clocks are thrown out of whack, it does more than disrupt sleep. Now, a new study from the United Kingdom adds more evidence that disrupting your body's clock may also be linked to mood disorders.

The study — which is the largest on this topic done to date with more than 90,000 participants — found that disruptions to the body's clocks were associated with a higher risk for mental health conditions, including depression and bipolar disorder. However, the researchers cautioned that the study found only an association between the biological clock and these conditions; it didn't prove cause and effect. [9 DIY Ways to Improve Your Mental Health]

The body's so-called master clock lies in an area of the brain called the suprachiasmatic nucleus. Using light cues from the sun, the master clock can figure out what time it is and relay that information to the "peripheral clocks" found throughout the body. Indeed, most cells in our body have a cluster of proteins that rotate on and off of each other to keep time throughout the day on a near-24-hour rhythm.

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In the study, which was published today (May 15) in the journal The Lancet, participants were recruited from the UK Biobank, a large project that took vitals and other health information from around 500,000 adults in the United Kingdom for future analysis and studies. From 2013 and 2016, more than 90,000 of these individuals were asked to wear accelerometers on their wrists that measured their movement for one week. In addition, the participants completed mental health questionnaires.

The study found that people with a greater disruption in circadian rhythms were more likely to have major depression disorder or bipolar disorder in their lifetime than those with less disruption. These individuals were also more likely to have mood swings, higher levels of neuroticism and loneliness, and lower levels of happiness and satisfaction with their health. What's more, people who had a higher disruption in their body clocks had slower reaction times than those with less disruption; reaction times provide an "indirect measure of cognitive function," according to a press release.

Aiden Doherty, a senior research fellow at the University of Oxford who wasn't part of the study, stressed in a commentary published alongside the study that the research cannot prove that circadian rhythm disruption causes mood disorders. Instead, it raises the question, "Does circadian disruption cause a decline in mental health status or vice versa, or are both due to some third factor?" he wrote.

Yasemin is a staff writer at Live Science, covering health, neuroscience and biology. Her work has appeared in Scientific American, Science and the San Jose Mercury News. She has a bachelor's degree in biomedical engineering from the University of Connecticut and a graduate certificate in science communication from the University of California, Santa Cruz.