Are You Sad? Maybe You Have SAD

Some people experience a serious mood change when the seasons change. They may sleep too much, have little energy, and crave sweets and starchy foods. They may also feel depressed. Though symptoms can be severe, they usually clear up. This condition is seasonal affective disorder (SAD). It usually happens during the winter. A less common type of SAD happens in the summer.

Patients living at different latitudes note that their winter depressions are longer and more profound the farther north they live. Patients with SAD also report that their depression worsens or reappears whenever the weather is overcast at any time of the year, or if their indoor lighting is decreased.

What causes SAD? Some experts think it's a lack of sunlight during winter, when the days are shorter. In the United States, it is much more common in northern states. Light therapy is the optimum treatment versus drugs or other modalities to intervene effectively.

There are three major dosing dimensions of light therapy, and optimum effect requires that the dose be individualized, just as for medications.

• Light intensity. The treatment uses an artificial equivalent of early morning full daylight (2500 to 10,000 lux), higher than projected by normal home light fixtures (50 to 300 lux). A light box should be capable of delivering 10,000 lux at eye level, which allows downward adjustments if necessary.

• Light duration. Daily sessions of 20 to 60 minutes may be needed. Since light intensity and duration interact, longer sessions will be needed at lower intensities. At 10,000 lux – the current standard – 30-minute sessions are most typical.

• Time of Day of exposure. The antidepressant effect, many investigators think, is mediated by light’s action on the internal circadian rhythm clock. Most patients with winter depression benefit by resetting this clock earlier, which is achieved specifically with morning light exposure. Since different people have different clock phases (early types, neutral types, late types), the optimum time of light exposure can differ greatly. The Center for Environmental Therapeutics, a professional nonprofit agency, offers an on-line questionnaire on its website, www.cet.org, which can be used to calculate a recommended treatment time individually, which is then adjusted depending on response. Long sleepers may need to wake up earlier for best effect, while short sleepers can maintain their habitual sleep-wake schedule.

On-going research is occurring to develop the most effective light-type of therapy for people who have SAD. “Recent research has emphasized that the human circadian rhythm system is differentially sensitive to short wavelength light. Light treatment devices using efficient light-emitting diodes (LEDs) whose output is relatively concentrated in short wavelengths may enable a more convenient effective therapy for Seasonal Affective Disorder (SAD).” (BMC Psychiatry 2007). The latest machine using the LED is known as the ‘Litebook’. Results of the research indicate that the Litebook is more convenience and more effective in treating SAD.

Source

National Institute of Mental Health