From correspondents in Washington, United States, 12:30 PM IST

Teens who experience negative emotions like fear, anxiety, guilt, shame, sadness or anger will potentially develop both anxiety and depression later.

Michelle Craske, psychology professor at the University of California, Los Angeles (UCLA), is four years into an eight-year study evaluating 650 students, who were 16 when the study began, to identify risk factors for development of anxiety and depression.

Participants placed in front of computers were told that they might receive as many as three small muscle shocks, each stronger than the last, when the screen became red and said 'danger'.

A countdown bar indicated when the shock was coming; as the bar counted down, the screen became redder. The students were also told that when the screen was green and said 'safe', they would receive no shock.

They then saw eight green and eight red screens, in random order, while researchers used sensors to study their physiological reactions, such as the 'startle reflex', which is measured by eye blinks, heart rate and sweat gland activity. Each participant actually received only one mild shock, during the fourth red screen.

All participants showed an elevated startle response when the threat of shock was most imminent, during the final countdown on the danger screens; this is the time at which the fear response is most imperative to survival.

However, those teenagers high in neuroticism showed a stronger startle response under conditions when the shock was not imminent and, in particular, during sections of the safe screens and the early phase of the danger screens.

Craske said 'it may represent a failure to distinguish conditions that are safe from conditions in which threatening events are very likely to occur'.

The study's co-authors included Edward Ornitz, professor at the Semel Institute for Neuroscience and Human Behavior at UCLA, and Bruce Naliboff, also of Semel.

Craske and her colleagues reported their findings this month in Biological Psychiatry.

(Staff Writer, © IANS)