Light Therapy

Overview of Light Therapy

In the early 1980s, Herb Kern, a research engineer, who thought that his annual cycle of depression might be caused by the shorter and duller daylight hours in winter, approached doctors working at the National Institute for Mental Health in Bethesda, USA. They proposed a treatment where he was exposed to light, equivalent to summer sunlight, for several hours each day. By the fourth day his symptoms had virtually disappeared (Lewy et al 1982). This was the start of our acknowledging the condition that has come to be known as Seasonal Affective Disorder (SAD). Seasonal Affective Disorder (SAD), or recurrent winter depression, is now considered a clinical subtype of major depression.

The criteria for Seasonal Affective Disorder (SAD), or "winter seasonal pattern", in the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, which are similar to other definitions of Seasonal Affective Disorder, specify a recurrent pattern of major depressive episodes during winter and remission of Seasonal Affective Disorder (SAD) symptoms during summer, in the absence of seasonal psychosocial stressors. Much of the interest in Seasonal Affective Disorder (SAD) has been stimulated by its response to exposure to bright artificial light. Clinical consensus guidelines have recommended SAD light therapy as a first-line treatment for Seasonal Affective Disorder (Lam & Levitt, 1999). Although light therapy may be regarded as a radical intervention for depression, in the case of Seasonal Affective Disorder (SAD) the use of SAD lights is rather common sense. Human beings are influenced by light. Light determines our sleep/wake cycle. In most animals and humans, the desire to sleep is brought on by the secretion of a hormone called melatonin. In the evening the pineal gland reacts to the diminishing levels of daylight and begins producing melatonin. melatonin is then released into the blood and flows through the body making us drowsy. Its secretion peaks in the middle of the night during our heaviest hours of sleep. In the morning, bright light shining into the eye reaches the pineal gland, which reacts by switching off the production of melatonin, thus removing the desire to sleep. The pineal gland communicates with the rest of the hormonal system. Consequently melatonin production also influences the functioning of other parts of the body. During darkness and sleep, melatonin modifies the secretion of hormones from organs such as the pituitary gland, the "master gland" of the hormonal system. The pituitary in turn regulates the secretion of hormones controlling growth, milk production, egg and sperm production. It also regulates the action of the thyroid gland, which is concerned with metabolism, and the adrenal glands, which control excretion of the body's waste. Further, it has been shown that light also effects levels of serotonin and dopamine neurotransmitters. The latter are connected with the Limbic system and the hypothalamus, which effects mood, emotion and autonomic systems, such as digestion. Therefore, fluctuations in light and darkness according to the seasons of the year influence rhythms of growth, reproduction and activity in animals and humans alike, and are the root of Seasonal Affective Disorder (SAD).

Statistics show that despite living and working in closed structures, our bodies still respond to the external environment and to its seasonal variability in duration and intensity. Studies have shown that growth rates in children are affected by the seasons. For example, surveys carried out in Germany, Sweden and Scotland show that height and weight increase is more predominant in the spring and early summer (Smyth, 1990). In many countries the rate of conception peaks in the summer when the hours of daylight are longest. In numerous trials the seasons have been seen to influence the timing and duration of sleep, pain threshold, alertness, eating habits, mood, the onset of menstruation and sexual activity. It is generally assumed that millions of years of evolution and adaptation have optimised human biochemical and physiological systems for function and survival under equatorial environmental conditions. Modern humans began their migration out of Africa only about 150,000 years ago. Little change in our "equatorial" systems might have been expected over this relatively short evolutionary time-span. Susceptibility to seasonal changes in mood and behaviour (that are found to extremes in Seasonal Affective Disorder) may reflect a genetic predisposition to an insufficient adaptation to temperate and high latitudes (Sher, 2000). Unfortunately, research has not yet been able to find a definitive aetiology for Seasonal Affective Disorder (Lam & Levitan, 2000; Lee et al 1998a; Mersch et al 1999; Sato 1997). Hormonal dispositions can explain perceived phenomena, yet, the systems involved are too complex to fully understand and thus predict cause and affect. Recent research has shown that Seasonal Affective Disorder (SAD) may be due to retinal sensitivity (Lee et al 1997), though more work needs to be done in this area.
Please note: If you are unsure of a SAD diagnosis or have contraindications then please consult with your GP/specialist before using a sad light box.

There are four classic symptoms experienced by Seasonal Affective Disorder (SAD) sufferers.
Extreme fatigue and lack of energy
Greater need for sleep and sleeping more than usual
Changes in appetite, especially cravings for carbohydrates and sweets, which can often lead to weight gain

Further, there are a number of other symptoms, which may be experienced by some sufferers.
Mood - sufferers tend to feel sad and low. They're often less interested in life and find it difficult to cope with everyday tasks. They may be irritable and short with friends and colleagues.
Sleep - sleep disturbance is common in SAD but varies from case to case - feeling excessively sleepy during the day is a common feature, and sleep is less satisfying.
Anxiety - tension, inability to cope with stress, phobias.
Loss of libido - decreased interest in sex.
Menstrual difficulties - pre-menstrual tension may be worse.
Feelings of hopelessness.
Increased sensitivity to pain - headaches, muscle and joint pain.
Other physical ailments - constipation, diarrhoea, palpitations.

Studies have shown that a large percentage of any given population, above or below 30 degrees of the equator, notice seasonal changes with regard to the above symptoms, to some degree (Rosen et al, 1990; Palinkas, 1996). This suggests that SAD is just one end of a spectrum of disorders, ranging from mild up to increasingly problematic symptoms (Kasper et al, 1989). People who suffer a milder form of the above symptoms are said to have ' sub-syndromal' SAD or S-SAD. Please note: If you are unsure of a SAD diagnosis or have contraindications then please consult with your GP/specialist before using a sad light box. Epidemiology of Seasonal Affective Disorder (SAD) & S-SAD Some psychiatrists are now suggesting that light therapy may be effective in treating nonseasonal, classical depression (Beauchemin & Hays, 1997; Benedetti et al 2001; McEnany & Lee, 1997) and patients in long term care (Lyketsos et al 1999). Daniel Kripke, MD, (director of the Circadian Pacemaker Laboratory at the University of California, San Diego) argues that light may produce antidepressant benefits within 1 week, in contrast to psychopharmacological treatments, which typically take several weeks. Indeed, a variety of studies have shown light therapy to be more effective in reducing depression than anti-depressants, though research is still in its relatively early stages. Wirz-Justice et al (1999) investigated the usefulness of light therapy in the setting of a psychiatric hospital, they found Daily self-ratings revealed positive effects of light (significant from day 5 onwards) with improved energy, sleep quality and shortened sleep latency with no change in sleep duration or the number of nocturnal awakenings. In a review of clinical trials, Kripke (1998) found that bright light therapy for nonseasonal major depression produced statistically significant net reductions in mood symptoms of about 12% to 35% on the Hamilton Depression Rating Scale. These results are comparable with those obtained in major trials of antidepressant medications. Light and medications appear to work best in combination, suggesting it would be advantageous to offer depressed patients speedy relief with light therapy while also starting them on medications that have more extensively verified efficacy. Combined treatment can lower costs because faster improvement means less disability and morbidity (Kripke, 1998).


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