New research has linked a brain hormone to panic attacks. Called orexin, this hormone is secreted in abnormally high amounts in those who suffer from panic attacks. Previous research showed that orexin regulates vigilance, arousal, wakefulness and reward and is located in the hypothalamus.

Panic attacks are a debilitating disorder that affect 6 million Americans. Symptoms can include shortness of breath, chest pain, palpatations, and is characterized by intense fear. Scientists from Indiana University and Lund University were able to trigger panic attacks by administering sodium lactate, a known orexin stimulant, in panic-prone rats.  Measuring the cerebral spinal fluid in 53 people with suicidal behaviours, those who had underlying anxiety disorders were found to have elevated levels of this hormone.

The lead researcher in the study, Dr. Anantha Shekhar  set out to block the secretion of orexin in panic-prone rats through a process known as RNA interference. The rats were divided into two groups – those receiving orexin blocks and those who did not. Both groups were then administered sodium lactate to induce anxiety behaviours. Those rats whose orexin was blocked, did not exhibit any signs of anxiety.

The study results are consistent with what we know about certain selective serotonin reuptake inhibitors (SSRIs) such as sertraline, (Zoloft). This popular medication  is used to treat anxiety as well as depression and previous research showed that sertraline  lowered orexin levels in cerebrospinal fluid while other types of antidepressants that work on different pathways, did not.

The hope is that by regulating the amount of orexin excreted in the brain, panic attacks can be successfully treated. The results of Dr. Shekhar’s study was released in the online edition of Nature Medicine in December, 2009. A more readable version of this study was published by the National Institutes of Health in January 2010.

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