Throughout life, different genes turn on and off. In the best-case scenario, genes make the right proteins at the right time. But if the genes get it wrong, they can alter your biology in a way that results in your mood becoming unstable. This biological tendency toward anxiety may be latent for years until an exceptionally stressful event triggers its expression. A person's genetic vulnerability is often intensified by anxiety-provoking behaviors learned in the family and stressful childhood experiences.
Still, much is unknown, and the genetic factors are hardly straightforward. Because anxiety and other mood disorders are thought to arise from genetic variations working in concert with life events and environmental factors, identifying the combinations that lead to anxiety, as well as depression, is quite challenging.
Researchers studying families with a history of anxiety disorders have scrutinized their genetic makeup in hopes of finding common features. Several candidates have been identified. Some are variants of genes, while others are regions on chromosomes that seem similar. For example, researchers found that a duplication on a region of chromosome 15 is especially common in families with high rates of panic disorder and phobia, according to one study. Potential genetic markers for panic disorder have also been found on chromosomes 1 and 11, and a possible marker for agoraphobia was found on chromosome 3. In addition, a study published in The Journal of the American Medical Association linked four of the eight variations of the FKBP5 gene with the more severe symptoms of post-traumatic stress disorder in adults who had suffered abuse in childhood.
But none of these genetic traits appears uniformly in people with anxiety disorders. Therefore it's unlikely that there's any single "anxiety gene." Many genes probably work together to influence the stress response, leaving us more or less likely to become anxious.