How we think and feel not only affects our waking lives, but also has a significant impact on our sleep, especially our ability to initiate and maintain the sleeping states. There has long been an established link between a large number of ‘mental health’ conditions and poor sleep.
In fact, one would be hard pressed to find anyone living with an enduring mental health condition who does not also have a co-existing sleep problem. Mental health conditions and insomnia almost universally seem to come hand-in-hand, with insomnia being a core diagnostic feature of many mental health conditions (e.g. major unipolar depression, bipolar depression, Lewy Body Dementia and so on). We also have good evidence for effective co-treatment (particularly for depression with co-morbid insomnia) (Manber et al.,2008), and emerging evidence for the co-treatment other conditions, e.g. people living with chronic pain and co-morbid insomnia (Tang, 2008).
There is an emerging school of thought that a large number of mental health conditions (notably those which tend to be acquired, e.g. depression and anxiety) rather than those to which people are more genetically predisposed (e.g. type 1 schizophrenia)) are regarded as disorders of memory. To expand and taking depression as an example of this: we know that people with depression are prone to a certain thought processes that are involved in the development and maintenance of the condition. These are referred to as ‘cognitive bias’ and ‘selective attention’.
Depressed people will tend to focus on negative situations or stimuli more than on more positive or neutral situations or stimuli (selective attention), and they will tend to see situations as more desperate then people who do not suffer from depressive symptomatology (cognitive bias). These two phenomena interact and, over time, can contribute to the maintenance and increasing severity of a depressive episode; and so lead an individual into a persistently and deeply depressed state of mind – major, clinical, unipolar depression. This process is almost always accompanied by poor sleep and, as mentioned above, insomnia is a core diagnostic feature of major depression.
Our mental health is driven by how we remember (and forget) things that happen to us in our everyday lives, and sleep is critical in these processes of the ‘memory’ and the ‘forgettery’. There is a very small part of the brain, right in the centre near the hypothalamus, called the hippocampus. When we are in deep sleep the brain is quiet and acquiescing, with the exception of the hippocampus, which is fully awake, up and running, firing on all cylinders, and at its most active in the 24-hour cycle.
We know from a large number of studies that the hippocampus is critically important for the consolidation of memory, acting as a control centre in the middle of the brain, sending messages out into the cortices above it. Taxi drivers whom have learned all the streets in London, referred to as ‘doing the knowledge’ have been shown to have larger hippocampi when training when compared to other people who have not had this training (Maguire et al., 2000). Chronic insomniacs have also been shown to have smaller hippocampi those of normal sleepers (Riemann et al., 2009).
These findings – and many others – have identified deep sleep as critical for the consolidation of memory. There is a useful analogy that can explain this a bit more. If you imagine that the inside of your head is a busy office, and that every thought that you have during the day generates a piece of paper in that office.
During the course of a day we have many, many thoughts, about everything and anything. Some of those things are important, or even very important (e.g. I need to call the mortgage adviser), but other thoughts may be less so (e.g. which socks shall I wear today?; Ooh – look at that dirty car). But each of these generates a piece of paper. Then we sleep and our secretary (the hippocampus) comes into the office and starts to organise things. This organisation consists of sorting through all the paper and throwing out the rubbish (socks / dirty car); and prioritising the important things (sticking the ‘call the mortgage advisor’ piece of paper on top of the in-tray for tomorrow morning) i.e. encoding this into the cortex as something to be remembered and not forgotten. If we sleep well we will do a good job of organising our office and it will be tidy again by the morning, if we do not sleep well then the office will be a mess in the morning.
There is the analogy for deep sleep and the hippocampus, but we are still left standing a bit as to where REM sleep fits into this picture. Some very recent work published in 2014 by Dieter Riemann, Kai Speigelhalder and colleagues from Freiberg in Germany has posited an advanced theory on the complex interplay between the memory, the forgettery, REM sleep and deep sleep. Their work is highly innovative and at the cutting edge of our understanding of the psychophysiology of sleep in health, and how it changes in poor health.
In order to explain this, we need to first examine the concept of schemas or frameworks. These will be familiar to many people, but, briefly for those unfamiliar with schemas another quick analogy.
If someone asks you to make them a cup of tea, and you have never done this before, it will be very difficult for you as you have had no experience in the task, no frame of reference, no ‘schema’ for making tea. If you are then taught to do this, you will have a framework in your head for what (and how) it is to make tea. Once in place, you will then find it much easier to make, say, a cup of coffee, as you already have a very similar schema established in your mind for making tea. Once practiced at making tea and coffee, you will then find it quite easy to make any number of hot beverages (hot chocolate, herbal tea, chai etc.) as your framework for hot drinks is well established in your mind.
We know from a large number of studies that learning is much improved after good sleep, and seriously impeded after poor sleep (and especially after no sleep). We are also pretty certain that this is why children need to sleep much more than adults do. This is also thought to be why infants will need to be asleep and awake multiple times in a 24-hour period as they have no schemas, and so need to assimilate much new information (and forget much irrelevant information) into their developing minds.
Enter Riemann and Speigelhalder and the interplay of REM sleep and deep sleep in this phenomenon. They suggest, from their own work and from reviewing the numerous studies published in this field over many years that, as we have seen, deep sleep is essential for the consolidation of memory, but also that REM sleep is critically important in the forgetting of irrelevancies (Landmann et al., 2014) or the ‘forgettery’. Forgetting some things may be just as ‘useful’ to us as remembering others.
If we reflect briefly on memory and schemas where we introduced the analogy of the sleeping brain being a cluttered office which is being ‘tidied’ of superfluous information. If our sleep is disturbed then this ‘clutter’ is not being fully cleared away before we awaken in the morning, leaving us feeling discombobulated with an ‘untidy’ office still in need of some spring cleaning. If we look at this in terms of slow wave sleep and REM sleep on the formation, integration and disintegration of schemas as proposed by Reimann’s group in 2014, then this idea carries some weight. In that, if we do not get enough good quality sleep to arrange our memories effectively during the night, then the consequences of this are potentially twofold.
Firstly, our schemas are not as well organised as they could be, and this ‘cluttering’ potentially aids in the precipitation and maintenance of a depressed mood; and secondly, that we begin to build new schemas that may be selectively attending and cognitively biased to negative situations or stimuli, and so the depressive state becomes self-perpetuating, even hard-wired into our neural pathways.
This idea is relatively novel, requiring further research to explore in detail and also explored for other mental health conditions, but the principle remains sound and extends beyond depression and into other mental health conditions. For example, people with depression (as above) will be developing schemas that selectively attend, and are more cognitively and emotionally biased towards, negative, threatening situations and events, which contributes further to the depression and to the strengthening of these schemas.
Depressed people tend to regard the world as a depressing place. The same is true for people with anxiety – situations and events are perceived as worrisome, events that others (in health) might regard as trivial, are regarded as threatening or dangerous in some way. People with insomnia often regard the bed as a place of arousal and distress rather than of solitude and rest, and they attend to sleep-related stimuli more so than people who sleep well (Speigelhalder et al., 2008). Those whom have a dependency on alcohol, or eating, or gambling etc. will have schemas that selectively attend to the environment and see opportunities to drink, eat, gamble etc. more so than those who are less dependent. They have schemas that attune themselves towards these particular stimuli.
The argument here is that over time we become hard-wired (neurones become laid down and organised in our brains) to selectively attend to, and to have emotional and cognitive biases towards, certain situations or stimuli. There are three old adages here that can perhaps contextualise this as part of a brief thought experiment: One: ‘everyone has their drug’, two ‘moderation in all things’, and three ‘we see the world through rose-tinted spectacles’.
By way of example: A small amount of alcohol consumption is not regarded as harmful, it is even seen as protective of health by some. Conversely, excessive amounts of exercise can be harmful (and are part of the diagnostic criteria for some of the eating disorders), but we are often told that alcohol is a bad thing and that exercise is good for us. If we are using alcohol, or exercise, (or whatever) to excess then we may be ‘over-attending’ to such an activity, and that leads to strengthened schemas for (and a cognitive bias towards) such activities and if these then start to predominate in our lives, then we may begin to ‘lose balance’ and our mental health can begin to suffer as a result.
So if mental health conditions can be seen as a disorder of memory, and if memory is schematically organised, driven and arranged; then sleep, which has such a pivotal role in that schematic organisation and arrangement, must be regarded as fundamental to the maintenance of our mental health, whether that be healthy or poorly, and everywhere else in between.
If you or someone you know is having trouble with either their sleep or another mental health problem and wants to speak in confidence then please do contact us for advice, guidance and signposting to appropriate services and professionals trained in the management of these conditions.
Further information is available in “Teaching the World to Sleep” by Dr David R Lee. 2016. Routledge, London. Available on Amazon at: http://tiny.cc/8qn3iz
References
Landmann, N., Kuhn, M., Piosczyk, H., Feige, B., Baglioni, C., Spiegelhalder, K., Frase, L., Riemann, D., Sterr, A., & Nissen, C. (2014). The reorganisation of memory during sleep. Sleep Medicine Reviews 18(6): 531 – 41. doi:10.1016/j.smrv.2014.03.005.
Maguire, E.A., Gadian, D.G., Johnsrude, I.S., Good, C.D., Ashburner, J., Frackowiak, R.S., & Frith, C.D. (2000). Navigation-related structural change in the hippocampi of taxi drivers. Proceeds of the National Academy of Sciences of the United States of America 97(8): 4398 – 403.
Manber, R., Edinger, J.D., Gress, J.L., San Pedro-Salcedo, M.G., Kuo, T.F., & Kalista, T. (2008). Cognitive Behavioral Therapy for Insomnia Enhances Depression Outcome in Patients with Comorbid Major Depressive Disorder and Insomnia. Sleep 31 (4): 489 – 495.
Riemann, D., Kloepfer, C., & Berger, M. (2009). Functional and structural brain alterations in insomnia: implications for pathophysiology. European Journal of Neuroscience 29(9): 1754 – 60. doi: 10.1111/j.1460-9568.2009.06721.x.
Spiegelhalder, K., Espie, C.A., Nissen, C., & Riemann, D. (2008). Sleep-related attentional bias in patients with primary insomnia compared with sleep experts and healthy controls. Journal of Sleep Research 17(2): 191 – 6. doi: 10.1111/j.1365-2869.2008.00641.x.
Tang, N.K. (2009). Cognitive-behavioral therapy for sleep abnormalities of chronic pain patients. Current Rheumatology Reports 11(6): 451 – 60.
