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Transient anxiety is a healthy response to stress. However, constant anxiety elicits negative responses and threatens an individual’s day-to-day living. The onset of anxiety disorders excluding specific phobias is often childhood to late adolescence or early adulthood. Though depression is characterized as a low-energy state unlike anxiety, there is a high concordance between anxiety and depression. “Nearly one-half of those diagnosed with depression are also diagnosed with an anxiety disorder” (“Facts and Statistics”). There are two goals of the study:

1. To compare the individual response levels between monozygotic (MZ) twins discordant for major depressive disorder (MDD) during an anxiety-provoking task.

2. To evaluate the relationship between self-report measures and physiological responses in adolescent MZ twins discordant for MDD. To identify how physiological responses vary between MZ twins discordant for major depression during a resting baseline and the 7.5% carbon dioxide (CO2) breathing challenge task.

The data was analyzed using multiple statistical methods including paired samples t-test and correlational models. We expected that MDD affected twins would self-report greater distress in response to an anxiety-provoking laboratory challenge and exhibit reduced physiological arousal. MDD affected twins demonstrated a somewhat reduced skin conductance response during the anxiety provoking task, suggesting blunted physiological response, which is consistent with other biological markers such as cortisol. There was a significant increase in sympathetic-vagal heart variability rate during the physiological baseline for the MDD affected twins. Although we did not observe any statistically significant differences for SUDS ratings assessed during baseline or inhalation of 7.5% CO2 enriched air, MDD affected twins reported higher levels of distress during the recovery period compared to their MDD unaffected co-twin. The results will shed light on the lasting impact of major depression on physiologic and subjective measures during rest and the biological challenge.

Publication Date


Subject Major(s)

Psychology, Psychiatry

Current Academic Year


Faculty Advisor/Mentor

Dr. Roxann Roberson-Nay


© The Author(s)

Anxiety Reactivity in Monozygotic Twins Discordant for Major Depression