Dolores O'Riordan. Picture: Bang Showbiz

Dolores O'Riordan drowned to death after accidental alcohol intoxication.

The Cranberries frontwoman was surrounded by five miniature bottles of spirits, a 35-centilitre bottle of champagne and medication packaging when she was discovered lifeless submerged in a bathtub at her hotel room in London's Park Lane in January, aged just 46, by a maid, Westminster's Coroner's Court heard on Thursday morning.

It was ruled at the hearing that the high levels of alcohol in the singer's body was a "high factor`' in the star's death. 

The courtroom also heard from Dolores' psychiatrist from back home in Ireland, Dr Ceallaigh, who stated that he believes she was suffering from an "an episode of mania or elevated mood" at the time of her death, Sky News reports.

The death was not treated as suspicious.

The 'Linger' hitmaker was laid to rest in January with a special service attended by close friends, family and the late star's bandmates at St Ailbe's Church in Ballybricken, Ireland, where Dolores first learnt to sing in the choir.

The singer's three children, Taylor, Molly and Dakota, were among the first to arrive and their father Don Burton - the singer's ex-husband and former Duran Duran tour manager - carried her coffin whilst the band's 1996 song 'Miss You When You're Gone' played.

In Dolores' honour, a guitar, a platinum disc award and a photograph of Catholic figure Our Lady of Dolours, who Dolores was named after, were placed at the altar as a mark of respect. 

Family members among the mourners included her boyfriend Ole Koretsk, her mother Eileen and her siblings.

The Cranberries band members Mike and Noel Hogan and Fergal Lawler - who together with Dolores released seven albums - also attended the mass.