Social Stress + Darkness = Increased Anxiety

Grillon and colleagues at the National Institute of Mental Health sought to examine whether stress increases unconditioned fear in humans. To do this, they measured the startle reflex of healthy volunteers in either light or dark conditions, and after either a socially stressful situation of public speaking, or after a period of relaxation.

The startle response is a sensitive tool for measuring anxiety levels, and in this study, was measured when volunteers were presented with white noise stimuli via headphones.

The authors found that the startle response was boosted when the volunteers were in complete darkness, and this effect was more pronounced after the stressor.

Dr. Christian Grillon, lead author on the project, explains, "Because stress has been linked to the precipitation of emotional disturbances, sometimes to a pathological level, it is important to understand how stress affects our brain and behavior." He adds, "We report that a mild acute stressor increases subsequent experimental anxiety in healthy subjects. The demonstration of stress-induced anxiety in the laboratory is important because it provides how stress alters nervous system function."

John H. Krystal, M.D., Editor of Biological Psychiatry and affiliated with both Yale University School of Medicine and the VA Connecticut Healthcare System, comments, "The authors show that social stress and darkness interact to increase the startle response. The refinement of this research method may help us to understand how threatening contexts and stressful social interactions interact at a mechanistic level to contribute to anxiety disorders."

Although this work is performed to further the scientific community's understanding of anxiety disorders, nearly all of us have felt scared or anxious in the dark at one time or another. So, the next time you check for monsters in the closet before climbing into bed, or when you peer into the dark bushes before your next "trick-or-treat," just remember that it's normal to jump when someone shouts "Boo!"

The article is "Acute Stress Potentiates Anxiety in Humans" by Christian Grillon, Roman Duncko, Matthew F. Covington, Lori Kopperman and Mitchel A. Kling. Drs. Grillon, Covington, and Kopperman are affiliated with the Unit of Affective Psychophysiology, Intramural Research Program, while Dr. Duncko is with the Section on Developmental Genetic Epidemiology, Intramural Research Program, and Dr. Kling is with the Mood and Anxiety Disorder Program, all at the National Institute of Mental Health, part of the National Institute of Health, Department of Health and Human Services, in Bethesda, MD. The article appears in Biological Psychiatry, Volume 62, Issue 10 (November 15, 2007), published by Elsevier.