Drugs deaths in Scotland will continue to rise, according to university research.

The study by the University of Glasgow's Centre for Drug Misuse Research said new factors were contributing to the death toll, including widespread suicidal tendencies among older addicts.

The research comes amid growing concern over drugs misuse in Scotland and in the Strathclyde area in particular which endured a record number of drugs-related deaths last year.

Within the largest police force area in Scotland, 148 people died of overdoses - a 50% increase on the previous year.

The prevalence of high purity heroin and the return of illegal tempazepam have been put forward to explain the scale of the death toll. But the new research points to other reasons.

A study of those who had taken near fatal overdoses showed that one in two addicts were suicidal at the time, two out of three had taken previous overdoses and four out of 10 were homeless.

Researchers said that older addicts, considered most at risk, should get priority from drugs services and hospital teams should have more resources to follow up those who take drug overdoses if the death toll is to come down.

Prof Neil McKeganey, head of the university research unit, said the study pointed to a pool of addicts in the west of Scotland who had been hooked for 10 years or more.

These people, said Prof McKeganey, were the most at risk of losing their lives.

He said: "Although it's shocking to say it, to reach a figure of 148 in a single year, that may not be the highest figure that we get.

"We may see a steady stream of figures of that kind over a number of years.

"If there were 5,000 (addicts), 15 or so years ago that really shows you there are potentially a lot of people now at very great risk of overdosing."

Dr Joanne Neill said she spoke to addicts in hospital soon after they had overdosed and found that one in two addicts wished they were dead.

She said: "The most significant finding was the very high proportion of people that we spoke to who had feelings of being suicidal at the point at which they took the drugs."

Drugs issues have never been far from the headlines in Scotland and the death of 15-year-old Coatbridge girl Kerry-Ann Kirk at Christmas reignited the debate as the death toll in Strathclyde hit a record level.

The teenage tragedy prompted massive reaction with ministers and police promising that the war against drugs would continue and anti-drugs activists calling for more action.