Application of light in the clinical environment

Winter depression

Winter depression is the most common appearance of seasonal affective disorder (SAD), in which symptoms occur on a nearly yearly basis during the short days of autumn and winter. Light therapy is the first choice of treatment for winter depression. Current practice is 30-45 minutes of high intensity white light in the morning. Adding more blue light to a polychromatic light source, also known as blue-enriched light, was not more effective than treatment with the original white light source; both treatments had high response rates after two weeks of treatment (ranging from 59% to 75%) (Gordijn et al 2012). Also at lower light intensities this blue enriched light has been shown to be effective in treating seasonal affective disorder (Meesters et al. 2011) and recently also treatment with blue light LEDs have been shown to be as effective as treatment with the regular white light boxes both for the full blown winter depression as well as in the treatment of sub-syndromal Seasonal affective disorder (Anderson et al . 2009, Meesters et al. 2016). In most cases, 1 week of light therapy at the beginning of the depressive episode is successful and prevents recurrence in that winter (Meesters et al. 1993, Knapen et al 2014). For some patients, probably with less severe complaints, the use of alarm clocks with light, the so called wake up lights, are equally therapeutically effective as the bright light boxes (Danilenko and Ivanova 2015).

The mechanism by which light therapy helps is as yet unclear. It has been hypothesized that the mood enhancing effects are related to the alerting effects of light as well as that the depressive symptoms can be the consequence of a disrupted circadian system and that light recovers a correct synchronization of rhythms (Lewy et al 2006, Terman et al 1998). However, others do not find any relationship between circadian rhythms, severity of complaints, nor between a shift in the rhythms and improvement with light therapy (Koorengevel et al. 2002, Wirz Justice et al. 1993). Although the efficacy of light treatment is undoubtable, the mechanisms by which it asserts its effects are continuously being investigated.


Non-seasonal depression

The reasoning behind light treatment for non-seasonal depression is that mood disturbances often coincide with sleep disturbances. Treating both the mood disorder and the sleep disorder may be the optimal way to combat depression. Positive results are described with effects of light treatment for non-seasonal major depressions that are equal or superior compared to those of pharmacological treatments (Lieverse et al. 2008; 2011; Lam et al., 2016).

Also in treatment paradigms of bipolar disorders during their depressive episode, light treatment is successful (Sit et al. 2007), but timing seems to be crucial to prevent patients from a switch into a (hypo) manic or mixed state. In combination with wake therapy (sleep deprivation) and medication, light treatment has been shown to be highly effective in the treatment of hospitalized bipolar disorders patients (Benedetti et al. 2014).

Since most clinicians are very careful to describe antidepressants to pregnant depressed patients, it seems very useful to try light therapy to treat antepartum depression. A first study of 5 weeks of light therapy in pregnant women showed promising results (Wirz-Justice et al. 2011).



Attention-deficit/hyperactivity disorder (ADHD) is a psychiatric disorder characterized by inattention and/or hyperactivity/impulsivity leading to impaired functioning. A large number of patients suffering from ADHD also suffer from seasonal affective disorders. The other way around is also true; in a population of SAD patients, a relative large proportion of the patients suffer from AD(H)D as well (Amons et al 2006, Levitan et al 1999, Rybak et al 2007). The eveningness chronotype is quite common in an AD(H)D population often leading to sleep onset insomnia (Van Veen et al 2010). With respect to the seasonality and diurnal preference in some of the patients suffering from ADHD, light treatment seems indicated and a first open trial of three weeks with morning light treatment showed promising results (Rybeck et al. 2006).



People suffering van Alzheimer’s disease and other forms of dementia can experience positive effects of light exposure. In general the majority of the people with dementia are of older age. This means that the light related effects on health for elderly people are also applicable. Next to the visual effects, studies demonstrated that light positively influence the non-image forming effects. In a long term study in a care facility people where daily exposed to, for indoors, extremely high light levels (Riemersma-van Der Lek et al., 2008), it was concluded that this light exposure had a modest effect on improving some cognitive and non-cognitive symptoms of dementia. Not only the light level seemed to influence the circadian system but also the spectrum of the used light. Blue enriched white light with a comparable light level as previous study, demonstrated  a positive effect on circadian stability and behaviour while under the normal color spectrum and light levels, no effect was noticed ((van Hoof et al., 2009a;van Hoof et al., 2009b). Whether or not dynamic lighting is beneficial is not (yet) confirmed by scientific evidence. In a study on the influence of light therapy among early Alzheimer’s living in their own dwelling, several circadian related effects where studied. A significant positive result of light therapy was found in reducing the risk to develop depression ((Møst, 2016).


Burnout can be described as emotional exhaustion, which ultimately leads to impaired functioning. Burnout is the response to prolonged job related stress. The percentage of employees developing burnout symptoms keeps on increasing. Studies on seasonal affective disorders (SAD) have shown that light treatment can be used to improve energy levels. Given the parallel in energy levels complaints between SAD patients and the energy levels in people suffering form burnout, it has been hypothesized that light could also be used as a tool to help those suffering from burnout. Although not many studies have investigated this topic, the evidence so far, showed improved energy levels in a small group of patients suffering from burnout after 2 weeks of morning light treatment (Meesters and Waslander 2010).

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