A New South Wales Coroner has found the conditions in a Sydney boarding house contributed to the deaths of six mentally-ill residents.

Six residents of the 300 Hostel in Marrickville died between 2009 and 2010.

Today the New South Wales Coroner Mary Jerram handed down her findings into the deaths, describing what she called a 'Dickensian' scenario where over-sedated people were reduced to a state of lethargy or inertia to keep them quiet.

The Coroner found the deceased each took two anti-psychotics daily and says the need for this medication was highly questionable.

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She found the administration of the drugs to three of the deceased impacted adversely on their mental and physical health.

The Coroner said the deaths were not caused by the hostel's conditions but were hastened by them.

Asha Ramzan's brother was not discovered for two days after he died at the boarding house.

She says medical professionals were complicit in what happened at the 300 Hostel - and she is concerned that they have gotten off scot-free.

"For our family, there is so much grief, and I'm not sure these are the answers we're looking for," she said.

The Coroner gave broad support for State Government moves to tighten restrictions on boarding houses.