The first United Nations survey of drug use in Kabul found on Thursday there are around 56,000 problem users of hashish, opium, heroin and pharmaceutical drugs.
The users turned to drugs to escape the traumas of war, poverty and unemployment, UN Office on Drugs and Crime advisor David McDonald said.
"Afghanistan has suffered war and conflict for over 20 years, many people here have chronic mental health problems such as anxiety, depression, post-traumatic stress disorder, insomnia, and so naturally people will turn to drugs as a way of trying to cope with their daily problems," he said.
The country's proximity to other nations with drug problems is also a contributing factor.
"Afghanistan is like an island surrounded by a sea of increasing drug use," McDonald said, naming Tajikistan, Iran, and Pakistan as guilty parties.
He added: "Problem drug use in Afghanistan is often ignored or there is a denial that there is a problem in Afghanistan at all. This is not the case."
Around 200 users and 100 key informants, such as health workers, were interviewed for the survery in February and March.
Mullah Omar's Taliban virtually
eradicated opium production
And a third of the interviewed users were women.
However, McDonald warned: "The actual number of drug users is likely to be much greater than those contained in this assessment."
While most of the opium and heroin produced in Afghanistan is intended for foreign markets, an increase in production means it is likely more drugs will end up in the local market.
Besides posing health risks, drug abuse is also a barrier to human and social development in Afghanistan, McDonald said.
"If you consider, for example, a family spending 20 percent of their monthly income on drugs, then this can have a devastating effect on household expenditure."
Opium cultivation was virtually eradicated in 2001 by the Taliban.
But since the regime's fall 21 months ago, Afghanistan has regained its place as the world's leading producer, accounting for 75% of global opium production.