Circadian Rhythm and SAD

Plants, animals and human beings are guided by day-night patterns. Our internal biological clock, called circadian rhythm, is attuned to sunlight. Plants and animals have long adapted themselves to lesser sunlight availability during fall and winter. They change their behavior during spring, when sunlight is abundant. Even horticulturists manage to get non-seasonal flowers by stimulating day-light conditions during winter periods.

The decrease in daytimes of fall and winter is associated with the mood of loss, sadness and laziness. People appear run down, gain in weight, and have difficulty to get out of bed as winter arrives. But in some people these symptoms get exacerbated and they feel depressed and incapacitated. This condition is called “Seasonal Affective Disorder” (SAD). Seasonal affective disorder is a type of depression which can affect daily routine.

SAD is caused by abnormal levels of chemicals in hypothalamus due to the restriction of daylight hours and the absence of sunlight in winter. Changing seasons have a direct bearing on our internal rhythm such as our set biological clocks inside. This rhythm is called circadian rhythm. This rhythm makes a shift as per sunlight patterns. As a result, our biological clock becomes out of ‘sync’ with our regular routines.

SAD and Light Therapy

Light therapy is also known as phototherapy or bright light therapy. The prevalent theory about light therapy is that an area of the brain near the visual corridor, the suprachiasmatic nucleus reacts to light stimuli by emitting out a signal to restrain the secretion of a hormone called melatonin. Cerebral data shows that there is impairment to serotonin operation in neurons leading to the suprachiasmatic nucleus. Reduced serotonin levels leads to depression. While facing bright light, such as that from a light box, the light energy will contain the melatonin secretion, thereby helping to control body's circadian rhythm and reducing symptoms.

Seasonal affective disorders can be solved by light therapy method that involves emitting visible light straight into the eyes to enable the light rays to stimulate pineal gland. Sun is the natural and perennial supply source of full spectrum light. SAD symptoms appear to subside initially after light therapy treatment, but these symptoms may return after discontinuation of light therapy. Counselors are advising SAD affected people to utilize the abundant sunlight that will be available during October to April season.

Light Box Method

The quantum of light needed differs among individuals. This therapy is generally undertaken in mornings. Therapy in the evenings may bring complaints of insomnia. Full spectrum light with UV light filtered is closest to natural light. Some suggest that ordinary fluorescent lights work equally well.

In the light box treatment, the distance at which the source of light meets the eye is important. One need not stare into the light, but occasional direct contact will be fine. One needs to sit at least for half hour to three hours a day. S itting tight for several minutes or hours is not a very enticing idea for people desirous of getting this treatment. For such people, there is an option of light visors. Staring at the light source may damage the eyes.

Professional psychiatric analysis should be done before going ahead with light box therapy. Other options are also to be thoroughly discussed and analyzed. It is better to keep it in mind that this type of therapy takes time and should be regularly treated. The therapist can provide several varieties of light boxes or visors that are available. It is to be noted that the time one spends in front of light is dependent on the intensity of light as well as the distance from the light source.

Side Effects of Light Therapy

Compared to side effects of antidepressant medications, the adverse effects of light therapy pale into insignificance. Even the mild effects are only temporary. Once light exposure is reduced, the effects will disappear. Some of the immediate effects are:

• Headaches or heaviness in head
• Eye itching, burning sensation, and tear accumulation
• Mild nausea
• Mild insomnia
• Irritability
• Mild euphoria
• Temporary vision disturbance
• Blurred vision
• Fatigue
• Mouth dryness

Precautions: People suffering from glaucoma, cataracts, and retinal detachment should not opt for light therapy. The bright light will exacerbate these eye conditions. People with diabetes and hypertension should get clearance from physicians before taking this light therapy. People should not opt for this therapy if their skin is sensitive to light.