People should consider light therapy for depression, according to Daniel F. Kripke, M.D., professor of psychiatry at the University of San Diego.  Since the early 1970s, Kripke has been studying the relationship between depression and biological rhythms.  He explained two theories of psychotherapy in an interview with the Psychiatric Times.

One theory claims that light affects mammals differently during different seasons.  More daylight in the summer causes mammals to have more energy, display bigger appetites, and show more sexual activity.  During winter, however, mammals experience losses of energy, sexual activity, and appetite because it becomes dark earlier.  Kripke concluded that light therapy might be an excellent way to treat depression.

The second theory is that depression could disrupt people’s circadian rhythms, and that light could correct them.  Kripke acknowledged that there is evidence for and against both theories.  Professionals have conducted several trials that have used light therapy to treat seasonal and nonseasonal depression in the United States, Japan, and Europe.

He reported that depressed patients sometimes responded more quickly to light therapy than to psychotherapy and medication.  With light therapy, some depressed patients started seeing results in a week or two.  A number of other patients have had positive outcomes by using light therapy in conjunction with psychotherapy and medication.

Light Therapy for Depression: Early Research

light therapy for depression

In the early 1980s, Kripke and his team conducted clinical trials using light therapy.  He found that light had an antidepressant effect on patients with major nonseasonal depression.  He concluded that the first seven patients experienced a significant reduction in their depression compared to people who used a placebo.  Each patient only had an hour of light therapy.

Kripke and his team conducted a one-week study in 1992 of fifty-one randomly selected patients who were suffering from major nonseasonal depression or bipolar-type depression disorder.  The patients were veterans hospitalized at a Veterans Affairs medical center.  The majority of patients experienced comorbidity, which means that they had depression and another condition, such as a substance abuse disorder.

Twenty-six of the veterans in the study were subjected to dim red light, while the other twenty-five were subjected to bright white light.  After a week, the twenty-five patients that used the bright white light experienced an 18 percent reduction in their depression, whereas the other twenty-six patients did not improve at all.

Light Therapy as a Possible Non-Chemical Solution for Depression

Kripke also worked with Richard T. Loving, Ph.D., R.N., and Stephen R. Shuchter, M.D., to study the effects of light on patients with major depressive disorders.  The patients used antidepressants with a half a night of sleep deprivation, followed by bright light therapy.  Researchers found that people who used bright light experienced significant reductions in their depressive symptoms in just one week.

Studies have found that sleep deprivation and medication can increase the response to bright light therapy.  Dr. Loving reported that within a week, patients who used all three combinations improved by 30 percent.  It was a dramatic improvement compared to patients who used antidepressants such as Prozac.  Many of these patients did not see results until twelve to sixteen weeks after they started using the medication.

Dr. Alexander Neumeister and his colleagues conducted a similar study at the University of Vienna that combined light therapy, sleep deprivation, and medication.  Neumeister found that this combination prevented a quick relapse of depressive symptoms for some participants.


depressed man

Combining Light Therapy and Standard Therapy for Depressive Disorders

Neumeister and his team conducted a study on people who had major depression.  The study exposed participants to light therapy in the morning after depriving them partially of sleep.  The purpose of this was to determine whether relapses of depression would occur after sleep deprivation.

Some of the participants in the study experienced reduced depressive symptoms, but the effects faded after the patients received a full night of sleep.  During the study, the participants used antidepressants along with light therapy, which prolonged the effects of partial sleep deprivation.

According to Kripke, clinicians should consider using a combination of light therapy and standard therapy when treating depressive disorders.  He would not suggest using light therapy by itself unless patients refused other treatments or could not tolerate conventional treatments.  Some patients in this category could be children whose parents are apprehensive about using antidepressants, patients who may have had allergic reactions to other medicines, and pregnant women.

Many People Do Not Know About Light Therapy for Depression

depressed person

Many people suffer from depressive disorders but do not seek standard treatment for various reasons.  If they knew about bright light therapy, they might consider it, said Kripke.  For his own patients who struggle with nonseasonal or seasonal depressive disorders, he has used a combination of light therapy, psychotherapy, and antidepressants.  He added that if patients’ disorders were severe, he would require them to arise in the middle of the night the day before they started light therapy.

Light therapy starts working for patients one to two weeks before antidepressants begin to work, said Kripke.  Patients who receive light therapy have the choice of using light from outside, light from indoor rooms, or specialized devices such as lightboxes.

In warmer, sunnier climates such as Southern California, people may be able to use outdoor light therapy, but in other environments, outdoor lighting might not be adequate or practical for therapeutic purposes.  Sometimes, increasing room lighting can do the job.  Or, buying a lightbox, a device that emits bright artificial light, could be an option.

Kripke said that people with depression who spend an hour or more outdoors might sleep better and experience reduced symptoms of depression.  He noted that while bright light is beneficial at any time of day, certain conditions could produce better results for certain people.  For example, people with seasonal affective disorder (SAD) may fare better if they use light therapy in the morning because people with the disorder often tend to sleep later.

Final Thoughts

On the other hand, people with bipolar disorder may fare better with light therapy during the evening, because evening light apparently triggers mania less than morning light.  But, professionals recommend that if people with bipolar disorder undergo light therapy, they should also use mood stabilizers, because light therapy also can trigger mania. Finally, according to Kripke and others, light therapy may be a promising tool to treat depressive disorders.

  • Loving, Richard T., et al. (2002, August 2) “Bright Light Augments Antidepressant Effects of Medication and Wake Therapy,” Depression & Anxiety.
  • Mendelson, Wallace, B., et al. (1999, May 1) “Light Therapy for Nonseasonal Depression,” Psychiatric Times.
  • Miller, Michael Craig (2012, December 21) “Seasonal Affective Disorder: Bring on the Light,” Harvard Health Blog.
  • Neumeister, Alexander, et al. (1996, January 1) “Bright Light Therapy Stabilizes the Antidepressant Effect of Partial Sleep Deprivation,” Biological Psychiatry.