Nearly 40 others were taken to A&E after taking the “party drugs”, while the mental health impact was so severe that more than 100 were admitted to the Royal Edinburgh’s toxins unit.
The shock statistics have fuelled fears that the city has a more acute problem with new psychoactive substances (NPS) than anywhere else in Scotland.
Edinburgh’s legal high problem is laid bare in a new report commissioned by the council, which says the six fatalities took place between January and October 2014.
It reveals there has been a “rapid increase” in the number of drug users mixing “legal highs” with heroin or other drugs and injecting them to create a lethal cocktail.
This is often taking place in the city centre, where shops selling substances are in “close proximity” to chemists which supply injecting equipment.
The dangerous trend – which has prompted community concerns about discarded needles being found in stairwells and parks – has also led to a spike in wound infections and diseases, including a rare strain of streptococcus.
Between April and October last year, the number of NPS users involved in a needle-exchange programme in the city almost doubled to nearly 600.
The corrosive powders – sold in “head shops”, online and reportedly in some newsagents – can also lead to abscesses and blown veins.
And police have reported a spike of “bizarre” and violent behaviour prompted by NPS – including the stabbing of an officer, a siege and a suicide.
Introducing the report, Edinburgh Alcohol and Drug Partnership manager Nick Smith writes: “The problems experienced by Edinburgh are not reflected in other areas of Scotland.”
Despite campaigns to tackle the “frightening scale” of the issue – including police and Trading Standards raids on shops last summer – enforcement action remains difficult due to the “legal” status of the chemicals.
Councillor Ricky Henderson, the city’s health leader, said: “That’s the challenge – everybody understands the term ‘legal highs’, but it’s a bit of a misnomer. Because of that nickname, people think it couldn’t cause any harm – but the evidence is to the contrary.”
He said an ongoing drive between emergency services, health chiefs and the council aimed “to prevent further figures, rather than highlight them”.
Officers are in talks with the procurator fiscal to explore ways of stamping out the availability of NPS, which often have colourful packaging.
Stimulants sold in a powder form with names such as Burst or Blue appear to be the most commonly used in Edinburgh.
Emma Crawshaw, acting chief executive of Edinburgh-based drug awareness charity Crew, said she had seen evidence of similar issues elsewhere in Scotland, and warned that NPS could lead to complex mental health issues.
“Use over a period of days can lead to stimulant-induced psychosis, especially if people are re-dosing without sleeping or eating,” she said. “Burst is an amphetamine-type stimulant and carries the same risks, especially if used in high quantities over longer periods of time.
“Mixing with other drugs is very common, especially alcohol, and increases health risks.”
Of the 835 admissions to the Royal Edinburgh’s toxins unit between March and August last year, 114 were referred after taking NPS.
And more than half of those patients, many of whom were drug users, had taken Burst.
Between January and October last year, police were called to 39 incidents where an NPS user had to be taken to A&E.
One of the alarming police incidents came in April last year, when a man who had been drinking and taking legal highs barricaded himself into his flat in West Pilton and threw furniture from the ninth floor, damaging two police cars in a 12-hour siege.
Superintendent Matt Richards said: “Frontline officers are trained to deal with cases where people have become aggressive and are acting in a chaotic and out-of-character way, but we are seeing an increasing link between this behaviour and NPS – and people being very unwell.”
Concerns about the impact that the use of legal highs is having on the wider community are also growing.
Independent councillor Jim Orr recently wrote to Justice Secretary Michael Matheson to raise concerns about the issue in his Southside ward.
He said: “This report reveals the frightening scale of NPS abuse in Edinburgh and how it has soared over the last year.
“I first became aware of the issue when significant numbers of used syringes started to get discovered around my ward, including in play parks.
“Now we have people shooting up in basement stairwells in squalid conditions.”