Teenage substance abusers display a characteristic pattern of heart rate and other physiological changes in response to loud noise, offering clues to how and why some young people develop substance use disorders, according to new research.
Those teenagers may use alcohol, tobacco, or other substances, in part, as a way to blunt their bodies' reactions to stressful events in their lives, Jeanette Taylor, William G. Iacono, PhD, and colleagues at the University of Minnesota, Minneapolis, report in the March issue of Psychophysiology, published today.
"Substance dependence is a complex phenomenon that cannot be fully understood through examination of single domains, such as the environment," Taylor says. "Our investigation lends further support to the growing literature that suggests that examination of physiological systems will provide important pieces in the puzzle of substance dependence."
While 175 young men aged 16 to 18 listened through headphones for a 90 decibel blast of white noise, Taylor and colleagues recorded a variety of physiological measures, including heart rate and skin conductance, an indicator of arousal. Sometimes the noise blasts would be signaled in advance on a computer screen; at other times they were not predictable.
When the noise blast was predictable, some of the young men responded with lower skin conductance readings than when the noise blast was unpredictable. These "good modulators," as the researchers called them, were least likely to be dependent on alcohol, tobacco, or other substances.
Other subjects had the opposite response: when the noise was predictable, their skin conductance readings were higher than when the noise was unpredictable. These "poor modulators" were the most likely to report symptoms of substance dependence.
Good modulators also showed increased heart rates in anticipation of the noise blast, but poor modulators showed no heart rate increase preceding the noise.
The findings are consistent with previous research suggesting that alcohol and substance abuse develop, in part, from defects in individuals' "inhibitory control system," leaving them prone to impulsive behavior. Good modulators in the experiment were able to take advantage of the signal preceding the noise blast and remain relatively unaroused, as reflected in their skin conductance readings. The poor modulators, in contrast, became more aroused in the face of the predictable noise blast.
The research was supported by grants from the National Institutes of Health and an Eva O. Miller Fellowship.
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