Sleep's connection to mental and physical wellbeing
Sleep disturbances can occur on their own, but in the vast majority of people poor sleep co-exists alongside mental and/or physical health problems. The traditional view was that poor sleep was simply secondary to these other issues and that by improving the so-called 'primary' illness, poor sleep would immediately resolve. Important research conducted in the last couple of decades has revealed a much more complex picture.
It is now known, for example, that poor sleep on its own can be a risk factor for developing future illness, as well as exacerbating existing health conditions. Experimental studies with healthy good sleepers, where total sleep time is restricted, indicates that lack of sleep (or certain stages of sleep), negatively impacts next-day emotional processing and mood, pain thresholds, immune functioning and glucose metabolism. Thus both 'mind and body' are affected by alterations to sleep quality.
Such work has led to the view that sleep disturbance may help to initiate, maintain or exacerbate additional health conditions, such as psychiatric/psychological disorders, chronic pain disorders, obesity and diabetes. One somewhat “roundabout” way to assess the impact of sleep loss on co-occurring physical and mental health problems is to treat the sleep disturbance with evidence-based treatments (like cognitive behavioral therapy) and then assess what impact sleep improvement has on the additional illness. Promising work has began to emerge showing that improving sleep can also have positive effects on both depression and pain. Of course, there are clearly health-conditions whereby sleep disturbance is almost characteristic (like in some pain disorders), and improving sleep can be very challenging. However, the preliminary evidence does indicate that even in these conditions, sleep quality can be improved, and this can be achieved through addressing sleep-related behaviors and thoughts, and helping to minimize the impact of sleep disturbance on day-to-day living.
It is also worth remembering that sleep research as an applied discipline is still in its infancy, and that as we continue to understand the functions of sleep, greater understanding of and ways of improving sleep disturbance will be achieved.