Introduction – Setting the challenge

Shortly after joining the SADA committee in August 2005 as the Association’s Science and Technical Officer, our Chairman, Jon Simmonds, asked me to look into the answer to 2 questions involving potential treatments for SAD. The first was with regard to the potential use of blue light and Light Emitting Diodes (LEDs) in the treatment of SAD and the second with regard to dawn simulation.

As a SAD sufferer myself, any developments in understanding and treating the disorder are obviously of particular interest and so I welcome the challenge enthusiastically. At first my progress was slow (you know how those of us with SAD suffer with the tendency to put things off in the winter!) and I found that I had a lot more to learn about the science behind SAD and the established facts about conventional white light treatment, before I could even begin to look at new developments in the field.

However the challenge has proven to be a fruitful one, and I am pleased to report that there have been some recent and exciting discoveries. I have been busy keeping the committee up to date on these and I am happy to now be able to share these with the rest of you.

Two years down the line and a significant amount of research later, I am now a lot closer to being able to answer those questions asked by Jon. I say “closer” because there are still many uncertainties in this area of science and questions remain unanswered even for the experts.

The most encouraging thing however, which I discovered much to my own surprise, is that there are experts out there, scientists from Europe and across the rest of the world, that remain committed to the battle to find out as much as possible about SAD and the benefits and disadvantages of different types of treatment. This should be a source of comfort to all of us and we should try to remember when we are feeling lousy, that this is still very much a live area of scientific research which will hopefully reveal some more of the answers we need, as time goes on.

The Questions – What I set out to answer

The first question I set out to answer, was what research has been carried out with regard to the use and effectiveness of blue and LED lighting in the treatment of SAD, in comparison to the fluorescent full spectrum daylight or white light lamps used in conventional light boxes.

The second question was whether dawn simulation can be described in itself as an effective treatment for SAD.

The Established Facts – What we already knew

Light therapy first became an option for the treatment of SAD following the discovery in the early 1970’s, that very bright light could influence the control of the hormone called “melatonin”. Melatonin is secreted by the pineal gland in the hypothalamus region of the brain.

The biological body clock known as the “circadian rhythm” is the way in which living organisms, including humans, have evolved to react to the 24 hour revolution of the earth causing a variation between light and dark and temperature at different times of the day. It has long been established that it is the hormone, melatonin, which controls the body clock in mammals.

Melatonin production is suppressed by early morning sunlight and this action resets the body clock on a daily basis. Melatonin is produced from the feel good hormone, “serotonin”, and if there is no effective suppression of melatonin, this leads to a high level of melatonin combined with a low level of serotonin. This in turn leads to symptoms such as depressed mood, lethargy, lack of energy, poor sleep patterns, loss of libido and carbohydrate cravings. In other words, the symptoms of SAD.

The reason for this is that people suffering from SAD need a higher intensity of light than other people to effectively suppress their melatonin levels and in order to prevent such symptoms. This is the reason why light therapy is an effective treatment for people who suffer the symptoms of SAD in the duller winter months. In fact, new research carried out in 2006, demonstrating the link between serotonin levels and our ability to appreciate the saltiness and bitterness of food, explains why carbohydrate cravings are so closely associated with SAD.

The important thing about conventional white light treatment is the intensity or brightness of the light that enters the eye. Light intensity is measured in “Lux”. The light on a summer’s day can be very bright, at least 10,000 Lux and sometimes as much as 100,000 Lux.

Until recently, all the research involving light therapy for the treatment of SAD has involved the use of full spectrum natural daylight or white fluorescent tubes. Using such light sources, the evidence shows that between 2,500 to 10,000 Lux of light must be received by the recipient of the light therapy in order for this to be an effective treatment for SAD. The necessary treatment time will depend on the intensity of the light used, and it is widely accepted that 10,000 Lux of full spectrum light needs to be received for a minimum usage time of 30 minutes in order to effectively alleviate the symptoms of SAD.

All of the above medical knowledge has now been established and accepted for 20 or so years, and it was from this starting point that I began my research.

AGM 2006 – The first piece of the jigsaw

For me, the first piece of the jigsaw in looking at new development, really fell into place at our AGM last year. We were extremely lucky to welcome Dr Stephanie Halford, from the Circadian and Visual Neuroscience Group at the University of Oxford, as our guest speaker. As some of you will remember, Dr Halford began her talk by explaining how our body clock or circadian rhythm allows our bodies to anticipate the daily changes in light and temperature, in advance of those changes happening, in order for the body to prepare itself accordingly.

While the role of the eye in mammals in detecting light for colour vision has long been known, Dr Halford told us that only recently has it emerged that the eye also performs as a role of detecting light for a range of behavioural and physiological responses that are distinct from sight. These responses include our sleep and wake cycle, body temperature, hormone levels including our melatonin levels, mood, altertness and performance, memory, heart rate and blood pressure.

The eye contains a layer of cells called the retina, a thin layer of interconnected nerve cells that cover the inside surface of the back of the eye ball. It has been known for many years that light is detected by two different types of photosensitive cells situated at the back of the retina, called the “rods” and “cones”. These are the cells which enable us to see objects and perceive different colours. However evidence for another light-sensing system in the eye which is unconnected with sight began to accumulate in the late 1990’s.

Dr Halford spoke to us about some research which has been recently carried out using laboratory mice which were generated so that they did not have rods and cones. When subjected to different amounts of light, these mice still have a circadian clock. In other words, the mice without rods and cones reacted to the varying amounts of light and this affected things such as their body temperature, hormone levels, melatonin levels etc. This led to the prediction that as the mice did not have rods and cones, which until that time were the only known light detecting cells in the eye, the eye must contain an unknown light detecting system that regulates the body clock.

Further scientific research has confirmed that there are indeed additional photosensitive cells in the retina which are different to the rods and cones and which control our body clock. These are known as the “ganglion cells” and they have been found to control melatonin production and suppression. Unlike the rods and cones, these cells are scattered throughout the retina and occupy roughly 2% of the surface area of the retina.

It has now been shown that the ganglion cells measure environmental brightness at dawn and dusk to keep our body clock in tune with environmental time. The way in which the ganglion cells control melatonin production and suppression is by the release of a protein call “melanopsin”.

In addition, the ganglion cells are responsible for the opening and closing of the iris in response to light intensity. The iris is the coloured circular muscle in the centre of the eye which controls the size of the pupil so that more or less light, depending on the conditions, is allowed to enter the eye.

In low light conditions, the ganglion cells send electrical impulses along the optic nerve to an area of cells also in the hypothalamus region of the brain, known as the Suprachiasmatic Nucleus (SCN) – this is the body clock. The SCN in turn controls the function of the pineal gland in the secretion of melatonin, as well as other responses such as body temperature, levels of other hormones, heart rate, blood pressure etc.

Interestingly, now we know that the body clock is not controlled by the visual pathway but by the ganglion cells, we know that it may still therefore be possible for blind people to benefit from light therapy.

It was clear from Dr Halford’s talk that the mechanism of melatonin production and suppression which has only been mapped out in the last 4-5 years, is groundbreaking work which has advanced scientific knowledge in this area considerably. Equipped with an understanding of how the ganglion cells in the eye had been discovered and their role in melatonin suppression, this enabled me to move forward with regard to looking at the research which has been carried out in respect of blue light and LEDs on the ganglion cells.

The First Question – Blue Light, LEDs and SAD

My next lesson was that following the discovery of the existence and role of the ganglion cells, even more recent research has suggested that melatonin suppression controlled by the release of melanopsin from the ganglion cells, is more effective under certain specific wavelengths of light. In particular, blue light was predicted to be most effective.

Bright sunlight peaks at 470 nanometres (nm), the blue part of the visible spectrum, with a second smaller peak at 540 nm, the green part of spectrum. Some recent research has indicated that it is light at 460-470 nm at the blue end of the spectrum which activates melanopsin production in the ganglion cells and that green light at 540 nm resets the receptor within these cells. Several other studies have been said to show that very low levels of blue light are therefore far more effective at suppressing melatonin than high levels of white light.

These discoveries about the potential importance of specific wavelengths of light, coincided with the invention in 2001 of a white light LED, which until that time had eluded science. Red LEDs such as those used in TV remote controls, have been around for at least 20 years. These were followed by green and amber and then blue LEDs, but until very recently no-one had figured out how to make white LED’s.

In basic terms, LEDs are tiny light bulbs that fit easily into an electrical circuit. Unlike fluorescent bulbs, LEDs only emit narrow spectrum light of a particular wavelength. They don’t have a filament that will burn out in time, and they don’t get especially hot. LEDs are much more efficient than white light or daylight tubes because they use one tenth of the power and also last much longer.

A white light LED produces light in a narrow range which peaks at 470 nm (blue light) with a second peak at 540 nm (green light) thus mimicking bright sunlight. White light LEDs produce very little light in the yellow to red end of the spectrum.

These further developments led to several clinical trials being carried out on the use of both blue and white light LEDs in the suppression of melatonin. The results of such trials suggested that light therapy using blue and white LEDs showed promise as an effective treatment for SAD.

It is these findings that led to the recent appearance on the market of a number of small and sometimes hand-held light therapy devices incorporating either blue or white LEDs as the light source. These products are advertised as effective in the treatment of SAD and are claimed to have a number of advantages compared to traditional light boxes such as the fact that they are more portable, use less power and do not require their bulbs to be regularly replaced.

The manufacturers of such devices claim that Lux is an inappropriate unit of measurement for melatonin suppression suggesting that it is the wavelength of light not the intensity that is most significant. Such manufacturers assert that traditional light boxes need to reach high levels of intensity to have a therapeutic effect and require a daily usage period of up to 2 hours, but that most of the light and the energy used to produce it, is wasted. They allege that the smaller LED products which emit a much lower intensity of light equivalent to around 5000 Lux, are more effective and have a therapeutic effect in as short a usage time as 15-30 minutes. In other words, the hypothesis of such manufacturers is that as long as the right wavelength of light is used a lesser intensity is equally effective.

It is here that the situation becomes more complicated. It is indeed true that there have been studies which have indicated that melatonin suppression is under the control of specific wavelengths of light, and that blue or white LEDs may be effective in the treatment of SAD. However, (and this is a big “but”) there does not yet appear to be enough scientific evidence to be sure of the effectiveness and/or any long term side effects of such blue or white LED devices in the treatment of SAD.

The first disadvantage of the clinical trials which have been carried out to date, is that most of them have been too small to give conclusive results, with often less than 30 subjects participating. The results of such trials must be interpreted with caution and the results of the trials indicate that larger trials are now required in order to provide more definitive information about the efficacy and safety of LED devices.

The second problem is with regard to the safety of such devices and the potential long term effects of using LED products. It is now widely accepted that traditional 10,000 Lux bright white light is safe. However questions have been raised about blue light safety and the use of white and blue LEDs, both of which emit light with peaks in the blue end of spectrum.

Light-induced photochemical damage to the eyes is particularly related to light at the blue wavelength. This type of damage to the retina is known as “blue-light hazard”. Older people are particularly susceptible to such light induced retinal damage.

Some manufacturers of LED products state that their devices have been approved by leading medical physicists, and that they have been certified as not exceeding the threshold levels for damage from blue light exposure set by international safety guidelines. The difficulty with this assertion however, is that individual susceptibility to blue light damage is so variable that these standards may not be able to presume to eliminate the risk to every individual, of acute damage from a blue light or LED device. In addition, the percentage of blue light entering the eye that reaches the retina may be highly variable from one individual to another. For these reasons, it may be difficult to calibrate a level of blue light that is both effective and safe for a wide range of individuals.

It should also be remembered that recent studies most certainly do not establish blue light or LED products as uniquely effective for SAD. Even the manufacturers of such alternative devices would have difficulty in discounting all of the valuable and universally accepted research regarding the use of bright white light. The consensus, at least amongst the scientific community (see below for further details), seems to be that before such a bold assertion regarding a higher efficacy of LED products can even be hinted at, then many further and larger studies with different comparison conditions must be carried out.

Due to the uncertainty surrounding the effectiveness and safety of blue light and LED products. SADA does not currently therefore recommend that members use such devices in the treatment of SAD until further research has been carried out.

The Second Question – Dawn simulation

The question as to whether or not dawn simulation in itself is an effective treatment for SAD has been a long standing issue of contention between the SADA committee and certain light box manufacturers whose products we recommend. The question is whether dawn simulation alone may constitute a treatment for SAD, in the absence of any light therapy or anti-depressant medication.

Dawn simulation is a technique using a light that comes on very slowly in the early morning, to imitate a natural sunrise. The key research finding is that our body clocks respond to this stimulus by speeding up and reinforcing the waking-up process, so that we have more or less woken up even before our eyes open.

There is much scientific research to show that the use of a dawn simulator may be useful in conjunction with light therapy and/or medication in the treatment of SAD.

Further, many members of SADA have reported that they have found a dawn simulator to be an invaluable adjunct to their light box.

In addition, there is also some scientific research which suggests that dawn simulation may be an active anti-depressant in itself which may be considered as an alternative rather than an addition to bright light therapy or medication. The problem with the studies which suggest this, however, is that they suffer from similar disadvantages to those explained above with regard to the clinical trials involving LED products.

The only conclusion that can therefore be drawn in this respect is that more, larger scale studies are needed to clarify the efficacy of dawn simulation as a free standing treatment. It is possible, for instance, that for suffers of SAD whose most prevalent symptom is hypersomnia, dawn simulation may be a suitable treatment whereas for suffers with different or more severe symptoms, this may not be sufficient treatment on its own. This possibility requires further investigation however.

Again, SADA does not therefore currently recommend that members use dawn simulators alone without using light therapy or medication in addition. It remains without doubt however, that a dawn simulator can be an invaluable addition to the tools which a sufferer uses to best cope with some of the symptoms of SAD, and I for one would not be without mine!

Society for Light Treatment and Biological Rhythms (SLTBR), Annual Meeting, June 2007, Copenhagen – Some further questions answered

As part of my research, I was lucky enough to be able to attend the annual meeting of the Society for Light Treatment and Biological Rhythms in Copenhagen earlier this year. The SLTBR meet every year, alternating the venue between Europe and Canada.

The SLTBR is the world’s leading body for light researchers. Its members include scientist from all over the world, including Europe, the USA and Canada. The SLTBR is a not-for-profit international organisation founded in 1988, dedicated to fostering research, professional development and clinical applications in the fields of light therapy and biological rhythms.

Members of the SLTBR have research and clinical interests in the healthy use of environmental lighting and in conditions related to light and biological rhythms including SAD, jet lag, shift work, sleep disorders, eating disorders, non-seasonal depression, bipolar disorder, and premenstrual syndrome. They study and use treatments including light therapy, chronotherapy (a technique for shifting waking and sleeping time), melatonin, serotonergic medications (medication containing serotonin e.g anti-depressants), and other treatments. The corporate members of the SLTBR develop and market devices for the scientific measurement and the therapeutic use of light.

At the conference, a number of renowned scientists spoke about the impressive research projects which they have recently undertaken and are planning to undertake with regard to a wide number of different effects of light. We heard about the way in which different levels of environmental light may affect cancer growth, the level of reproductive hormones, and homicide and suicide rates. It was also very exciting to learn about the possibility that light therapy may in the future be used not only in the treatment of SAD but also in the treatment of personality disorders, night eating syndrome, ADHD and non-seasonal depression, as well as help weight loss. The conference even heard about the way in which light may be used to treat the disruption of the body’s circadian rhythm during travel in space!

One of the most educational aspects of the conference was learning about the lack of and need for more large scale, well designed trials to produce more conclusive results. It was explained that there are numerous difficulties in designing rigorous clinical trials involving light and light therapy.

For example, all scientific experiments require a control condition or “placebo” to compare the effects of light to condition with no or less light. However in order for the results of the experiments to be reliable and unbiased, the subjects taking part in the experiments should not be aware of whether they have been subject to the active or controlled conditions. While it is simple to create a placebo tablet which is inactive but visually identical to an active tablet, it is not very easy to find a controlled condition when the active condition is bright white light - in other words, the subject will know whether or not they have been subjected to bright light and this may affect the results of the experiment. Placebos which have been used in clinical trials involving light include negative ionisers and dim red or green light.

Furthermore, not only are there a lack of willing participants for clinical trials, those who are willing to take part may not be suitable if they are suffering from other conditions or illnesses which may affect the results of the trial. These are known as “exclusion criteria” and anyone suffering from such conditions will not be able to take part. In addition there is also a lack of resource and funding and many of the trials are only conducted over a very short period of time.

What really struck me in Copenhagen however, is how lucky we are that despite the odds and challenges faced, there remain a body of international scientists who continue to forward the pursuit of increased knowledge in the area of light, light therapy and circadian rhythm, of all which are of course very significant to sufferers of SAD. It was very clear to me that this is still an incredibly active area of scientific research and that in turn, this is leading to all sorts of discoveries regarding types of light therapy and light therapy devices.

Whilst at the conference, I was able to gain further insight into the questions I had set out to answer, as many of the people present were the ones who had made some of the discoveries in the first place. In particular, I learned about the scientific view regarding the use of blue light and LEDs in the treatment of SAD.

The message which came across loud and clear in this respect, is that we simply do not know at the moment what the answers are or what the future may hold. There is undoubtedly an agreement that blue or LED light is potentially at least as effective as bright light in the treatment of SAD, but there is also agreement that without further research we cannot be sure of this or indeed of any potential disadvantages or side effects of such treatment.

Experts at the conference pointed out that more, longer and longer scale trials are desperately needed and that we should be cautious of rapid attempts to convert from traditional white light treatment to blue or LED light treatment. The warning not to underestimate possible blue light damage to the eyes was also driven home. It was explained that another factor which should be taken into account is that we do not yet know whether light in the blue wavelength has any effect on medication. In addition, we were reminded that light works on the brain in many different ways and circadian rhythm is probably not the only mechanism to be considered.

It is therefore invaluable to remember if considering any alternative light treatment device, that although the manufacturers may quote scientific proof of the safeness efficacy of such devices, the scientists are still clearly reserving judgement.

Another aspect of the conference was some simple, practical tips on how to minimise the symptoms of SAD by considering the effects of our every day environmental lighting. For example, it was pointed out that many computer screens emit a high intensity of blue light. Using a computer before bed time may therefore lead to melatonin suppression and trick the body into thinking that it is morning thus causing disturbed sleep. This of course may also apply to people who do not suffer from SAD, but in SAD sufferers who already experience disrupted sleep patterns, this may serve to worsen the problem. Equally watching TV before going to bed may have a similar effect. Along the same lines, it was suggested that many of us sit in the office during the day in poor lighting and then in the evening, sit in our lounges in low level lighting. However just before we go to bed, we go into the bathroom to brush our teeth or into the bedroom and switch on a bright light. This means that in fact we may be receiving the highest intensity of light at the end of the day, again leading to poor sleeping patterns.

These observations all seemed obvious to me when pointed out but were not necessarily things I had thought about before. Actively thinking about and trying to avoid such negative effects of environmental lighting may therefore have a positive impact on our every day lives. I for instance have taken to brushing my teeth in the dark, much to the amusement of my partner!

It was a great privilege to be able to meet and listen to some of the most eminent scientists in their field, talking about there most recent research projects and their plans for the future. Being able to attend the SLTBR’s annual meeting was a very valuable experience and I learnt an awful lot about light treatment and the different uses to which it may be put. More than anything however, I learnt that the experts remain committed to continuing to build upon the knowledge we already possess and to improving the lives of people such as ourselves, for whom light treatment is essential. For that, if nothing else, we must be extremely grateful.