Washington, Jan 7 (IANS): The drug overdose epidemic will peak at about 50,000 annual deaths in 2017 before declining to a non-epidemic state of approximately 6,000 deaths in the year 2035, says a US-based study.

This is the first to apply Farr's Law on the rise and fall of epidemics to an outbreak that is not, strictly speaking, infectious in origin, the researchers noted.

"To some extent, drug use is a social behaviour and has the potential to spread like a contagious disease among individuals in a network," explained first author Salima Darakjy, a doctoral student at Columbia University's Mailman School of Public Health.

At present, more than 40,000 people in the US die every year by unintentional drug overdose -- a number that has ballooned tenfold since 1980.

In a study of smallpox in the mid-1800s, pioneering British epidemiologist William Farr discovered that the rate and duration of the epidemic's rise was mirrored in its decline.

The researchers believe the rate of deaths from prescription painkillers, which account for two-thirds of all the deaths, has already slowed.

Tighter rules on painkillers have led some users to switch to heroin, which is cheaper and more readily available.

But while this substitution effect is concerning, it is unlikely to alter the course of the epidemic, the researchers noted.

On the other hand, the epidemic of drug overdoses -- like most epidemics -- would not end by itself. Public health efforts must continue even as the epidemic wanes, they added.

The study appeared online in the journal Injury Epidemiology.