The brains of 34 intravenous drug abusers, who had mainly used heroin and methadone, were examined after death and compared with 16 young people who had not used drugs.
This revealed that the drug abusers sustained a level of brain damage normally only seen in much older people and similar to the early stages of Alzheimer's disease.
"Our study shows evidence of an increased risk of brain damage associated with heroin and methadone use, which may be highest in the young, when individuals are most likely to acquire the habit" says co-author Jeanne Bell Professor of Neuropathology at the University of Edinburgh.
Damaged nerve cells were identified in the key areas of the brain involved in learning, memory and emotional well-being.
"We found that the brains of these young drug abusers showed significantly higher levels of two key proteins associated with brain damage" adds Professor Bell.
"In a previous study we found out that drug abuse causes low grade inflammation in the brain. Taken together, the two studies suggest that intravenous opiate abuse may be linked to premature ageing of the brain."
The 34 documented drug users had a history of opiate abuse - mainly heroin and methadone - but were HIV negative and had no history of head injury. The 16 control cases had no history of drug abuse or neurological impairment.
The average age in these two groups was only 26 years and included drug abusers as young as 17.
Tau protein, which in its soluble form is essential for communication and transport within brain cells, had become insoluble in some cells, causing nerve cell damage and death in selected areas of the brain.
Other nerve cells showed an accumulation of the amyloid precursor protein, which suggests that protein transport had been disrupted and the nerve cell functions affected.
"This study shows that drug abuse can lead to a build up of proteins which cause severe nerve cell damage and death in essential parts of the brain. This is very worrying as there are strong indications that drug use in the UK, in particular opiates like heroin and methadone, has continued to rise in recent years" says Professor Bell.
"The drug abusers we looked at in the study sadly died at a young age, but there are many others who don't realise the long-term effects that these drugs may be causing."
The research was supported by the Medical Research Council (MRC), which is funded by the UK Government, and the US National Institute on Drug Abuse (NIDA).
Further information and press copies of the paper are available from:
Annette Whibley, Wizard Communications
To interview Professor Bell please contact
Linda Menzies, University of Edinburgh
Notes to editors