Many teens struggle with depression or anxiety, but may not realize that what they are encountering is more than typical teenage angst. Much of the confusion may come from a general belief that the teenage years are filled with mood swings and overwhelming social situations, from dating to friendships. However, some adolescents experience emotional struggles that are more than just the result of a combination of frustrating circumstances. Some may be dealing with symptoms of clinical depression or anxiety and require medical treatment. While many cases of teen depression and anxiety go untreated, a new study may provide insight into how to screen teens for the disorders. A team from the University of Cambridge has identified a biomarker that can identify teens that are at an increased risk for developing anxiety or depression. The biomarker found by the researchers is a variation on a gene, the short form of the serotonin transporter called 5-HTTLPR. It was identified as a marker for anxiety and depression in a group of 238 teens, all aged between 15 and 18. The participants each were given genetic testing with an environmental assessment. The researchers then conducted a computer test to examine how the participants received and handled emotional information. The teens were asked to rate words as positive, negative or neutral (for instance, "joyful" was considered to be a positive word, while "range" was a neutral word). The participants who were found to be both homozygous for the short allele of the 5-HTTLPR transporter struggled to evaluate the emotional association for the words. This may indicate a difficulty in processing emotional cues. Additionally, those teens also had been exposed to sporadic family arguments for at least a six month period and had been a witness to parental violence prior to the age of six. The results add more information to previous research that had shown a connection between a disturbed perception and emotional response with a higher risk of developing anxiety and depression. Because of the findings, the researchers believe that the problems with processing emotional and cognitive responses may be interpreted as an in-between marker for the development of depression and anxiety in individuals who are genetically predisposed and who have experienced negative emotional situations during childhood. The test used in the study may provide an opportunity for a low-cost screening tool for identifying adolescents most at risk for developing anxiety and depression. It could allow for early intervention among those who are at an increased risk for developing one of the disorders. Ian Goodyer, M.D., principal investigator in the study, explained that a person often develops depression or anxiety because of the way they tend to think of themselves during a negative event. Patterns of negative thought may extend to how individuals think of themselves. The study's findings appear in a recent issue of the journal PLoS One.