Rome, May 3 - Drug use among Italian teenagers remains relatively unchanged from the previous years at roughly 20% and is concentrated on marijuana use, according to a study released on Friday. Over 500,000 smoke marijuana out of a population of 2.5 million adolescents, said an Italian report for the European School Project on Alcohol and other Drugs (ESPAD), conducted by the clinical physiology arm of Italy's national research centre CNR. Researchers found a 0.6% increase in marijuana consumption compared to the previous survey. Roughly 60,000 Italian teenagers used cocaine and 30,000 consumed opiates, the survey found. Heroine use remained steady, edging up by 0.1%. Stimulants gained somewhat in popularity. Of those surveyed, 3.8% said they had popped a stimulant at some point in their lives and 2.6% said they had within the last year. In the preceding survey, 3.6% had tried uppers at least once and 2.4% admitted to popping within the previous year.