Swinburne University of Technology - Melbourne Australia

Good vibes need a body clock on song

Story by Bianca Nogrady

Underneath the normal disorder of everyday lives there is a steady, strong and immutable beat that never changes. It is the pulse to which every living thing on the planet sets its rhythm of life, and it has been there since the very creation of our planet - the rising and setting of the sun.

Swinburne University of Technology researcher Dr Greg Murray has keenly studied the body clock or, in technical terms, the circadian system, and found its rhythms can have profound effects on human mood.

It is worth pointing out that Dr Murray knows a lot about rhythm. He was a professional drummer until his early 30s, when he shifted his focus from one rhythm to another - musical to biological.

The research he has done since then has shown a definite connection between the body clock and certain psychological responses, including the capacity to trigger relapses in patients with bipolar disorder.

But what is our body clock and, more importantly, what is its 'tick'?

"Virtually all organisms, including humans, have adapted an internal timing system to predict the daily change from light to dark," says Dr Murray, senior lecturer and convenor of Clinical Psychology Programs at Swinburne. "The circadian system enables the organism to prepare for, and not just react to, this dramatic change in the environment."

In humans, the master circadian clock is found in a small group of cells that sits deep in the brain above the pathway from the eyes to the brain. These cells are light-sensitive, enabling the clock to 'tune' itself to external cues, particularly sunlight. The 'tick' of the clock is a molecular pulse generated by the cells which, in turn, triggers the expression of various biochemical signals that control a large number of body functions including body temperature, metabolism, blood pressure and heart rate. But, most importantly, those signals tell the body when it is time to sleep, and time to wake up.

Mood disorders such as bipolar disorder have long been linked with 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," he says.

Dr Murray and his PhD student Ben Bullock have just finished putting this theory to the test in a project funded by beyondblue, the National Depression Initiative. Twelve volunteers with bipolar disorder were fitted with wrist-worn devices designed to monitor their circadian system by measuring their physical activity throughout the day and night. These actigraphs, while fairly crude, give a useable measure of circadian output under natural conditions, Dr Murray says.

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," Dr Murray says. 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.

"With Dr Indic Premananda, from the University of Massachusetts, we are analysing the actigraph data to find the time scale at which rhythm disruption is most apparent."

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 "We're also interested in the clinical application of this research and we are working with Swinburne's commercialisation unit, Swinburne Knowledge, to identify potential industry partners."

Human body clock research has applications far beyond bipolar disorder. Another, much larger, group in society also seems to operate on an abnormal circadian timetable, much to the annoyance of their parents and teachers. Teenagers are often maligned for their unconventional and antisocial sleeping habits, but Dr Murray says they are not to blame. "We know that adolescents need almost as much sleep as primary school kids do." However, teenagers experience a 'phase delay' in their circadian rhythm, so instead of being ready for bed at about 9 to 10pm, they do not get sleepy until 11 to 12pm, leading to potential problems with school times, which stay the same or become even earlier.

Dr Murray's student Dr Suzanne Warner has confirmed a link between the loss of sleep created by this school schedule and poor performance and mood at school. This link has been observed by other groups, and has led some school districts in the US to shift their school hours to accommodate the sleeping schedules of their students.

But even in healthy adults with normal sleep habits, the circadian rhythm appears to exert a subtle but discernible influence on mood from one hour to the next, according to Dr Murray's latest research, funded by the Australian Research Council. "With the University of Melbourne, we've recently shown that the clock drives how proud people feel, for example. It is remarkable that such human experiences are affected by a primitive system for predicting sunrise."

With so many facets of the circadian rhythm to explore, Dr Murray has turned to a major international group to help him expand the research. The Division of Sleep Medicine at Brigham and Women's Hospital (BWH) in the US, an affiliate of Harvard Medical School, is home to the world's major circadian and sleep research centre, having collected and analysed circadian data on literally thousands of people.

With Dr Steven Lockley, who leads the Circadian Physiology Program in the Division of Sleep Medicine, and Dr Janis Anderson, director of the Seasonal Affective Disorders Clinical Services at BWH, Dr Murray has begun 'mining' the data, looking for links between neuroticism and the amplitude, or 'strength', of the circadian clock rhythm.

"Dr Murray is exploring novel questions about how the circadian system affects psychological health that we have not previously considered, and it is exciting to see where the answers will lead," Dr Lockley says. "We hope that this is the start of a long-term collaboration with Dr Murray's group, which might see joint experiments and eventually lead to students travelling between our laboratories."

The collaboration opens a new door for Dr Murray and his research, allowing him to explore the fundamental question of what is a normal versus an abnormal circadian rhythm. "The Harvard group has made groundbreaking discoveries about the nature of the human body clock, but they hadn't really considered the implications of differences between people. We now have the opportunity to refine our understanding of individual differences in circadian function and how these relate to mood and wellbeing."

Tips for teenagers

With exam time approaching, Dr Murray shares some tips on how to improve sleep during adolescence

During the day

• Get outside during the day, preferably early in the morning, but lunchtime will do
• Get some exercise each day, but finish your exercise at least three hours before bedtime because elevated body temperature is a barrier to sleep
• Avoid napping
• Avoid caffeine (coffee, tea, soft drinks, chocolate), nicotine and other stimulants after noon

Around bedtime

• Aim for 8.5 to 9.25 hours of sleep a night
• Choose a bedtime that works for you, and go to bed at this time each night
• If at the drinking age, avoid alcohol - although it makes us sleepy, it shortens and disrupts sleep
• Avoid overstimulation later in the evening - intense study, computer games, arguing or heated discussions are incompatible with sleep
• Develop a soothing pre-sleep routine to train the body into a relaxed state for bed - try a warm bath, a quiet read, camomile tea, or a relaxation technique in the hour before bed
• Create a good sleeping space that is dark, comfortable, cool, quiet and uncontactable, which means no mobile phones and no internet
• Avoid bright light in the evening - screens, especially computer screens at close range, tell the body clock that it is not yet dark
• If you have any worries or concerns at bedtime, write them down for consideration in the morning
• If you are not asleep 20 minutes after lights out, get up and do something quiet until you feel tired

In the morning

• Open blinds or turn on lights as soon as you get up - the body clock benefits from a 'light reminder' that the day has started

Catch-up sleep

• Weekend sleep-ins are OK, but do not awaken more than two to three hours later than your usual awakening time or it could disrupt the body clock

Is poor sleep a problem for you?

• Effective, practical strategies exist for treating most sleep problems. If your sleep quality is consistently poor or is causing distress, you should seek professional assistance.

For more information about managing sleep and beating stress in adolescence, visit the Swinburne Psychology Clinic website, www.swinburne.edu.au/lss/psychology/pc/