Opioid pills. Photo: John Moore/Getty Images
The team concluded 232 deaths could have been caused by people taking too many drugs they were given by health professionals in England over a 15-year period between 2000 and 2015.
It is the first time that the medication history of opioid-related deaths have been studied in such detail.
And the researchers say changes need to be made to how opioids are prescribed in the light of their findings - while suggesting patients need to be more aware of the potential dangers of the drugs as well.
What did the researchers find?
The University of Manchester research team, led by Dr Teng-Chou Chen, studied half a million electronic health records.
The study reveals around 25% of the 232 patients who died from opioids between 2000 and 2015 had not been prescribed the drugs for pain 12 months before their death.
Around 35% of the patients had been prescribed high dose opioids of 120mg a day in the 12 months before their death.
Opioid related deaths are rare but can result from high opioid prescribing.
The study has been published in the British Journal of Anaesthesia.
What do the results mean?
The researchers, who also include scientists from the University of Nottingham, have suggested the results show the people involved stockpiled previously-prescribed opioids or had been given them from people they knew without realising the dangers of taking high combined doses.
Those who were already on a high dose and then took additional pills probably suffered unintentional death.
Most of the overall opioid-related deaths occurred between the ages of 30 to 50.
Around 55% of them were men, 30% had a history of substance abuse and 80% suffered from psychological illnesses.
Is this still going on now?
Although the data is six years old, the team argues there is no reason to think the situation will be any different today.
The researchers are particularly concerned as the amount of this medication which is prescribed has grown significantly over the past decade.
What exactly are opioids and what do they do?
Prescription opioids are mainly used for pain relief and work on the central nervous system by attaching receptors to our brain cells, releasing signals that block pain.
The most common include morphine, tramadol, fentanyl, codeine, and oxycodone.
Overdoses can cause respiratory depression, drowsiness, fatigue and falls.
Respiratory depression is the most common cause of death in opioid overdose, though symptoms of drowsiness may mask it.
What do the researchers say?
Dr Teng-Chou Chen from The University of Manchester said: “Our research clearly shows that opioid prescribing could be linked to patient deaths in England.
“This is worrying as we already know that prescribing for these drugs has increased hugely over the past decade.
“Chronic pain, often accompanied by anxiety and depression, is a serious public health problem and makes the lives of millions of people a misery.
“People desperate for pain relief seemingly take whatever opioids they can find whether prescribed or not.
“They may stockpile prescribed drugs, or get them from friends or neighbours. Some obtain them online. But the terrible consequences of doing this are now very apparent.”
He added: “Psychotropic medicines, such as gabapentinoids and antidepressants are commonly prescribed for patients with chronic pain.
“Our study also showed an increased risk of opioid-related death when opioids were co-prescribed with those psychotropic medicines, even though in most cases, people were prescribed opioids with a lower daily dose.”
The team is now calling for changes in the guidelines governing the use of opioid and the way they are monitored.
Dr Li-Chia Chen, from The University of Manchester who leads the research team, said: “There is actually is no evidence to suggest that opioid-based painkillers are able treat many complex long-term pain conditions, though if used appropriately for acute pain such as surgical pain they are extremely helpful.
“We think the guidance for doctors on opioid dosing should be much more detailed. But patients too need more knowledge about the dangers of overdosing on these drugs.
“We also believe better monitoring and systems should be in place for the disposal of these drugs.
“And clinicians should think very carefully about opioids prescribed ‘as required’, because these often stay in the cupboards of patients and are never returned to pharmacies.
“Most importantly, patients need to be offered other alternative options for managing their chronic pain, as the recent NICE chronic pain guidance suggests, and avoid long-term pharmacotherapy as a mainstay for chronic pain management.”