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Feeling low? It might not be depression.

Some Perth people have been taking anti-depressants for years, only to find that they are suffering from a sleep problem, not a mental illness.

Obstructive Sleep Apnoea (OSA) and depression share many symptoms, and practitioners say it is difficult to know whether the sleep disorder is part of depression or whether depression is a symptom of OSA.

A collaboration of UWA researchers including psychologists, a neuropsychiatrist and respiratory and sleep physicians, are comparing the two conditions to be able to more accurately  identify, diagnose and treat the disorders when they occur together.

They will also examine the efficacy of Continuous Positive Airway Pressure (CPAP) therapy - used to treat OSA -- in reducing depression associated with sleep disorders.

The diagnosis of depression in patients with OSA is confounded by the overlap of symptoms between the two disorders: excessive daytime sleepiness, fatigue, loss of interest, decreased libido, poor concentration and sleep disturbance.

"This increases the risk that depression may be overlooked or inappropriately treated," said Professor of Psychology Romola Bucks. "It remains unclear whether OSA causes depression or is simply associated with it."

David Hillman, Clinical Professor in Pulmonary Physiology and Sleep Medicine, and an expert in sleep disorders, said he and his colleagues "frequently see patients who have very clear sleep apnoea but have borne the label of depression for several years.

"When they tried CPAP therapy and got a good night's sleep, it was as if a cloud had lifted.  Obstructive sleep apnoea was their problem, causing them to feel depressed. CPAP can work extraordinarily quickly and relieve the symptoms attributed to depression," he said.

"Very high depression and even suicidal and self-harm tendencies can disappear with CPAP.  We have some very powerful data that attests to this. The bottom line is that Obstructive Sleep Apnoea is a physical problem which is addressable."

Obstructive Sleep Apnoea is the most common sleep disorder affecting Australians (about six per cent of the adult population). People with the disorder momentarily and frequently stop breathing while sleeping.  In severe cases, they can have hundreds of ‘obstructive events' (with the soft palate obstructing the airways) every night.

When they stop breathing, there is no oxygen going in, no carbon dioxide going out.  The stress responses and lack of oxygen can put people at an increased risk of stroke, heart attack and diabetes.  Sufferers are also more likely to have accidents during the day, including fatal ones, on the road and at work when they ‘nod off ‘, because they are so tired.

"It can also affect you cognitively, specifically your memory," said Professor Bucks. "It has been argued that lack of oxygen and repeated awakenings during sleep could lead to brain damage."

Continuous Positive Airway Pressure therapy (CPAP) is delivered through a sleep mask which keeps up a continuous flow of oxygen to the wearer.

Sleep disorders seem suddenly to have become the most talked-about and diagnosed medical problems of this century. Professor Bucks and Professor Hillman agree that the ageing population, coupled with our alarming tendency towards obesity, has accelerated the incidence of OSA and other sleep-related problems.

"As people age, their throat muscles become floppy and can obstruct the airways," Professor Hillman said. "And problems can also develop among people who work out in the gym, doing heavy static weight training which results in a heavily-muscled neck. Those big lumps of muscle present a high risk of OSA."

The team is recruiting volunteer patients from the sleep clinic at QEII to take part in a trial using CPAP therapy to determine its effects on depression symptoms.

To help define which symptoms to focus on, information about depression symptoms and sleep apnoea in the general population will be obtained from recruits in the Busselton Health Study.  Professor Alan James, a respiratory and sleep physician, has been involved with the Busselton study since 1989.  In 2009, he helped to set up the Busselton Healthy Ageing Study, which is collecting data from 4,000 ‘baby boomers' (people born between 1946 and 1964).

"We are asking for information about sleepiness, sleep behaviour and depression, hoping to find what symptoms are common to OSA and depression and which symptoms are specific to each disorder," he said.

Professor James said the collaboration, despite being spread across faculties, campuses and even the State, with work being done in Busselton, was very productive.  "It has been exceptionally well organised by the study's chief research officer, Peta Grayson, who brought all the protocols together. Dr Nigel McArdle, who works in the same area as David and me, has been invaluable in developing the protocol, carefully anticipating problems and defining CPAP outcomes, based on his previous experience in trials of CPAP.

"We have all felt an overwhelming wish to achieve the best possible results, which is why this collaboration has been so successful and even enjoyable," he said.

Sergio Starkstein, Winthrop Professor in Psychiatry and Clinical Neurosciences at Fremantle Hospital, brings his substantial experience in assessing depression in the setting of other illness to the study. He said it was not unusual for him to see a patient who had been referred to him for treatment for depression, who actually had OSA.

"These patients tell me they have no energy, they can't concentrate, they have no motivation, they want to sleep during the day.  But they don't say that they are feeling sad or anxious. And this is the clue that the patient may not actually be depressed but be suffering from OSA," Professor Starkstein said.

Interestingly, these patients do not complain of insomnia, so they are not aware that their sleep is being disrupted hundreds of times every night.

Professor Starkstein said there was a chance that people with undiagnosed and untreated OSA could develop full-blown depression. "So it is very important to identify the two disorders.

"This study is designed to help us to do this."

Dr Michael Hunter, the senior scientist and coordinator of the data collection team in Busselton, and Professor Matthew Knuiman from the School of Population Health and who will oversee the data analysis, complete the study team.

By Lindy Brophy

Published in UWA News , April 2013