People living in poorer areas of England are prescribed more heavy duty painkillers than those in wealthy regions.
A study has found patients in the north are prescribed nearly four times as many opioids – such as codeine, tramadol and morphine – as those in the south.
Doctors in Blackpool and St Helens, Merseyside, dole out the most prescriptions for the controversial drugs.
And these same areas are among the least well off and least healthy across the country, which researchers said shows health inequalities and a north-south divide.
Experts suggest higher levels of taxing manual labour, smoking and depression could contribute to people in the north suffering more pain.
Researchers at the universities of Nottingham and Manchester delved into NHS GP prescribing figures for Birmingham, Manchester, Newcastle and London.
They found eight of the 10 areas with the most prescriptions were all north of Nottingham, with one in the East Midlands and another in East Anglia.
The lowest number of opioid prescriptions was in London. There are four times fewer opioids prescribed in the least affected areas than the most, the study claimed.
Opioids are among the strongest painkillers used by the NHS but – as members of the same chemical family as heroin – are highly addictive.