The Coolmine Therapeutic Centre, which treats people for drug and alcohol addiction, saw a 42% increase in addicts seeking its services last year.

The centre's annual report shows that 1,350 people were supported by Coolmine in 2015 through their community, day and residential programmes.

168 men are said to have resided in Coolmine Lodge in 2015, while 81 women resided in the centre's mother & child facility at Ashleigh House.

Coolmine’s Chairman, Alan Connolly, told Newstalk Breakfast that one of the biggest challenges the centre and its clients faces is in relation to housing.

"Clients will spend a minimum of five months in residence, and then there's step down and after care for seven months," he explained. "That's a huge commitment. The biggest obstacle to their long-term recovery is a lack of housing".

Mr Connolly said the question of housing supply must be solved to prevent people in recovery returning "to a drug addiction environment, a difficult family, or even living rough and being homeless".

While the centre says that the level of heroin addiction is growing, they also found that there has been an increase in poly drug use - or a combination of drugs - and alcohol.

Mr Connolly says they particularly noticed an increased intake of clients using benzodiazepine last year.

"They're prescription drugs, given out by GPs and maybe sold on or stolen," he said. "It's not illegal to have them on your person.

"Addiction is addiction, [and] these are very addictive drugs. Coolmine is committed to the total abstinence of illicit drugs and alcohol - but what we're saying is that abstinence isn't enough. It's abstinence in the context of a fulfilled life for clients," he added.