Britons were fretting about the decline in civility two decades ago, when muggers and heroin addicts roamed the streets.

ECONOMIST: A new worry, and a new political buzzword

Some blame Hollywood for the increase of young heroin addicts, citing use by actors including Christian Slater and Robert Downey Jr.

CNN: Heroin use on the rise

The researchers included the methadone patients for comparison because this drug (used for pain relief and to wean addicts off heroin) is known to prolong QT interval.

BBC: Heart risk link to SSRI antidepressants confirmed