Depression is the number 1 psychological disorder in the western world and it is growing in all age groups, in virtually every community, and the growth is seen most in the young, especially teens. At the present rate of increase, it will be the 2nd most disabling condition in the world by 2020, behind heart disease.
While there may be many factors contributing to this increase, one often unrecognised cause is sleep, or lack thereof. Many of us today are far too busy in our 24/7 world of light and activity to get the 7-9 hours sleep we need each night.
In fact over the last fifty years we have decreased our average sleep time by about 20% and today many of us get less than 7 hours of sleep on a regular basis.
It has long been recognised that depression can cause sleeping problems but it is often not realised that the relationship is bi-directional. In other words, poor sleep can also cause the onset of depression.
A study published in 2011, which followed more than 7000 people for a minimum of 12 months, showed that those who reported sleep difficulties were five times more likely to develop depression than those who reported good sleep.
Why is this so? Well, sleep very much affects how we view ourselves and the world around us. Studies have shown that the level of self–esteem and optimism is highest in those who regularly get between 7 – 9 hours of sleep each night and lowest in those who get less than 6 hours.
It has also been found when we don’t get enough sleep we preferentially remember negative events and have minimal recall of positive events, creating a falsely negative view of ourselves and of the events in our life.
This negative perspective is further exacerbated by the effect insufficient sleep has on our brain’s emotional centre. Most of us know that when we don't get enough sleep we are more likely to be inpatient, lose our temper, or just generally be in a bad mood.
Without good sleep the connectivity between the brain’s emotional centre and the part of the brain responsible for good decisions is reduced or lost.
This means that instead of rationally considering our responses we are more likely to react directly from our emotional centre so that we react emotively to even a minor provocation.
This reaction increases the level of our stressful hormone, cortisol. As cortisol increases, our feelings of stress also increase, leading to a state of hyperarousal making sleep even more difficult. If we continue in not getting enough sleep, before too long a bad and difficult day turns into a week or two of difficult days and for too many of us depression will eventually follow.
To ensure that we are the happiest and most optimistic version of ourselves and to get the most enjoyment from life we need to get 7-9 hours of sleep every night.
So take care - next time you decide to cut back on your sleep remember that it may have a bigger effect than just making you feel tired the next day.
Dr. Carmel Harrington joined us at the 
in 2015 to present on how to improve sleep quality and performace.
Dr Carmel Harrington has been researching sleep for 20 years. She has written books on the topic and advises companies and educational institutions on sleep health. She is an Honorary Research Fellow at the Children's Hospital Westmead, a member of the Australasian Sleep Association and the Sleep Health Foundation.
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