An estimated quarter of a billion people between the ages of 15 and 64 years, abused at least one drug in 2014 but that figure and the number of drug-related deaths have remained relatively steady over recent years, according to a U.N. report published Thursday.

At the same time, the U.N. Office on Drugs and Crime said that the number of in the United States in 2014 was nearly triple that of 2003 with five times as many deaths related to the drug than in 2000.

UNODC put all drug-related fatalities at an estimated 207,400 worldwide in the 15-64 age group while recording a significant drop of poppy cultivation in Afghanistan, the key provider of opium base.

Overall opium production last year fell by 38 per cent from the previous year to the late 1990s level of about 4,770 tons, says the report. It attributes that to a 48-percent decline in Afghanistan, "mainly as a result of poor yields" in the south of the country.

The report also notes a slight increase in coca bush cultivation but says the area used for this is the second-smallest since the late 1980s.

Among synthetic drugs, the report said that 75 new psychoactive substances were reported in 2015 with data still being collected for that year. That compares with a total of 66 for all of 2014.