Light Therapy
Niloufar Niakosari Hadidi
This chapter provides a definition and overview of light therapy, its history, cultural applications, and scientific basis. It further expands on the use of light therapy to treat seasonal affective disorders and identifies other health conditions for which light therapy could be beneficial. Techniques that could be used by nurses educated in its practice, precautions, and recommendations for future research are provided.
DEFINITION
Light therapy is defined as daily exposure to full-spectrum or bright light to treat conditions such as seasonal affective disorder (SAD). This needs to be differentiated from phototherapy, which is used to treat conditions such as hyperbilirubinemia or psoriasis (Lam, 1998). This chapter focuses on a description of light therapy as used in the treatment of SAD.
Seasonal affective disorder (SAD) is a mood disorder that occurs more frequently in the dark winter months and disappears spontaneously in spring. However, it has been found to occur with less frequency in summer, and can occur repeatedly year after year. According to the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5; American Psychiatric Association, 2013), SAD is categorized as an indicator of major depression; patients with SAD experience episodes of major depression that tend to recur at specific times of the year (American Psychiatric Association, 2013).
These seasonal episodes may take the form of major depressive or bipolar disorders. Many symptoms of SAD are similar to symptoms of nonseasonal depressive episodes: low mood (often without prominent diurnal variation), loss of interest, anhedonia, anergia, poor motivation, low libido, anxiety, irritability, and social withdrawal (Eagles, 2004). More than one half of patients with SAD experience an increase in sleep duration with poor quality. Further, about the same numbers of patients experience increases in appetite and weight gain and have cravings for carbohydrates and chocolate (Eagles, 2004). Symptoms often start in autumn and winter, peak between December and February, and then subside during spring and summer.
Prevalence rates of SAD have been estimated to be between 0.4% and 5% in the general population with symptoms present for approximately 40% of the year; and these patients experience significant morbidity and impairment in psychosocial function (Kurlansik & Ibay, 2012; Westrin & Lam, 2007). SAD is reported to be more prevalent in women than in men and among younger age groups (MacCosbe, 2005). The exact causes of SAD are unknown; however, research has demonstrated that reduced sunlight may disrupt the circadian rhythm that is responsible for the body’s internal clock (Edery, 2000). The disruption of this cycle may lead to depression.
History of Light Therapy
Since the beginning of time, people have realized the healing power of light. The history of light therapy goes back to ancient Egypt, where sunlight was used for medical treatments. Healing temples were built with colored crystals that were affixed on the surface of stone walls so that they were aligned with the sun’s rays. People would lie down on benches and their bodies would be immersed with pure or colored lights (Curtis-King, 2008). Later, Hippocrates described the use of sunlight to cure various medical disorders. Although ancient Romans and Arab physicians had no scientific explanation for light therapy at the time, they knew that the healing power of light was helpful for medical treatments (Curtis-King, 2008).
In the early 1980s, researchers discovered that specialized bright light (20 times brighter than normal indoor light) was the most effective treatment for winter depression (Kripke, 1998a). Now research is confirming that this light is effective in improving the symptoms of nonseasonal depression as well (Kripke, 1998b). In fact, a systematic review of 62 reports on the efficacy of light therapy on nonseasonal depression found it to be effective and an excellent criterion to include in treatment of nonseasonal depression today (Even, Schroder, Friedman, & Rouillon, 2008). Light therapy has been reported to have a 70% positive response (Miller, 2005).
SCIENTIFIC BASIS
Research has demonstrated that individuals with SAD are positively affected by light (Flory, Ametepe, & Bowers, 2010; Golden et al., 2005; Gordijn, ‘t Mannetje, & Meesters, 2012; Meesters, Dekker, Schlangen, Bos, & Ruiter, 2011), sometimes as immediately as after even one light therapy session (Reeves et al., 2012). Light plays an important role in secretion of melatonin, as well as serotonin.
Melatonin is a natural hormone produced by the pineal gland, a peasized structure located at the center of the brain. Melatonin synthesis is stimulated by darkness. When light enters the retina, it stimulates the hypothalamus and inhibits the pineal gland from converting serotonin to melatonin (Miller, 2005). It is important to note that the impact of melatonin on circadian rhythms is compromised by cardiovascular and neurodegenerative diseases as well as aging (Altun & Ugur-Altun, 2007).
Although studies suggest that administering melatonin supplements at night may help individuals with disrupted circadian rhythms, in a recent meta-analysis of the impact of melatonin on sleep, the authors suggested that melatonin results in only a 2% to 3% improvement in sleep efficiency (Brzezinski et al., 2005).
Lewy and colleagues (1995) report that taking melatonin supplements and exposure to bright light may change the circadian rhythm and melatonin secretion. The authors suggest that light therapy and melatonin administration could be helpful for winter depression, jet lag, and shift work.
INTERVENTION
Technique
The recommended device for provision of light therapy is a fluorescent light box that produces light intensities of greater than 2,500 lux (Westrin & Lam, 2007). Lux is a unit of illumination intensity that corrects for the photopic spectral sensitivity of the human eye. To better understand the concept of lux, indoor evening room light is usually less than 100 lux, whereas a brightly lit office is less than 500 lux. In contrast, outdoor light is much brighter: a cloudy, gray winter day is around 4,000 lux and a sunny day can be 50,000 lux to 100,000 lux or more (Westrin & Lam, 2007). The most effective dose has been reported to be 10,000 lux for 30 minutes daily; lower intensities (i.e., 2,500 lux) can also be effective, however, they require longer durations of 2 to 3 hours (Terman & Terman, 2005). It is recommended that broad-spectrum white light from fluorescent lamps in which the ultraviolet (UV) and infrared (IR) light are being filtered be used because UV and IR wavelengths are
potentially damaging to the eyes (Howland, 2009). Although earlier studies indicated that bright light therapy did not benefit nondepressed individuals without history of SAD (Avery et al., 2001; Kasper et al., 1989), a recent study reported improved mood and vitality more than 1 month after using 1 hour of bright light exposure daily in healthy individuals. This effect was enhanced by the addition of physical exercise to light exposure (Partonen & Lönnqvist, 2000).
potentially damaging to the eyes (Howland, 2009). Although earlier studies indicated that bright light therapy did not benefit nondepressed individuals without history of SAD (Avery et al., 2001; Kasper et al., 1989), a recent study reported improved mood and vitality more than 1 month after using 1 hour of bright light exposure daily in healthy individuals. This effect was enhanced by the addition of physical exercise to light exposure (Partonen & Lönnqvist, 2000).
It is recommended that patients diagnosed with SAD start light therapy in the fall and continue until symptoms are resolved in the spring or summer (Kurlansik & Ibay, 2012). Light must enter the eyes for light therapy to be effective in the treatment of depressive conditions; however, the person should not be looking at the light directly. The result of several clinical trials has led to the recommended dose of 10,000 lux for 30 minutes soon after awakening in the morning (Terman & Terman, 2005).
The light enters the eye, and is transmitted with nerve impulses to the pineal gland, which controls melatonin secretion. Patients often report relief of depressive symptoms in 3 days to 4 days. The time of the day is also an important consideration in light therapy. Often, light therapy is administered in the early morning on arising. Using a pooled clustering technique of 332 patients from 14 research centers across 5 years, Terman and colleagues (1989) concluded that early-morning exposure was more effective in reducing depression than when administered at other times of the day.
Whereas the exact mechanism of light therapy is unknown but believed to be through an ocular process, extraocular transcranial phototransduction in mammals results in changes in reproductive cycles and increased serotonin levels in the brain (Campbell, Murphy, & Suhner, 2001). Based on this information, Timonen and colleagues (2012) have hypothesized that light therapy may be effective if delivered in methods other than through eye mediation. They conducted a pilot study in 22 physically healthy patients with SAD in whom light therapy (6.0-8.5 lumens) was administered via earplugs in bilateral ear canals for 8 to 12 minutes per episode 5 days a week for 4 weeks. This study was conducted during the darkest part of the year in Finland. Seventy-seven percent of the subjects experienced full remission of SAD symptoms (Timonen et al., 2012). Ninety-two percent of the subjects achieved at least a 50% reduction in self-reported anxiety symptoms. These preliminary results in this pilot study challenge the existing model of light therapy mechanism of action, warranting further exploration.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
