High blood pressure can cause damage to the heart and blood vessels in teenagers just like it affects adults, a study has warned. The damage can occur at blood pressure levels that are below the clinical definition of hypertension in youth, researchers said. High blood pressure in youth is defined differently than it is in adults. In childhood, high blood pressure is based on percentiles, rather than blood pressure level. Researchers from the Cincinnati Children's Hospital in the US looked at whether organ damage in teens develops below the 95th percentile, which is the clinical definition of high blood pressure in youth.