Researchers at Swinburne University of Technology have studied the body clock or the circadian system and found that its rhythms can have profound effects on human mood, including triggering relapses in patients with bipolar disorder.

According to them, mood disorders such as bipolar disorder have long been linked to sleep problems, suggesting that the circadian system plays a role in these conditions. "If you take seriously this idea that the body clock is part of a causal pathway to mood disorders, then a natural deduction is that monitoring clock function might provide early warning of relapse in vulnerable people," Greg Murray, the leader of the research team, said.

For their study, the researchers recruited 12 people with bipolar disorder and fitted them with wrist-worn devices designed to monitor their circadian system by measuring their physical activity throughout the day and night.

The study subjects were tracked for up to 12 months. In that time, one participant experienced a serious relapse that landed him in hospital. "For our purpose, it was very interesting that circadian activity data really did show a marked signal of deterioration in the days and even weeks before the relapse.

"Instead of his activity patterns operating on a 24-hour cycle, the participant shifted to a 48-hour cycle of wakefulness and broken, disturbed rest," Murray said. In the next stage of research, the team wants to see if signals of rhythm disruption in patients can be used as markers of vulnerability to bipolar disorder in the general population.