Seventy per cent of people admitted to the major not-for-profit rehab centre Odyssey House, based in Sydney, in the past financial year listed alcohol as among their reasons for seeking treatment.
For almost one in three (29 per cent), alcohol was their primary addiction - up from 28 per cent in 2006-07 and 20 per cent in 2005-06.
Amphetamines such as speed, ecstasy and ice accounted for 23 per cent of Odyssey's admissions in 2007-08 followed by heroin (19 per cent).
Alongside the increase in alcohol-related admissions, Odyssey House chief executive James Pitts said people with addictions were also increasingly likely to suffer a mental illness.
Almost half (44 per cent) of the 715 men and women admitted to Odyssey's residential, detoxification and rehabilitation programs last financial year said they also were depressed or they suffered from anxiety, schizophrenia or bipolar disorder.
This was up from 30 per cent in 2005-2006, and just 10 per cent in 1998-1999.
"If this upward trend continues, more than half our clients in 2009 will have a co-existing mental illness, putting added pressure on our services and our staff," Pitts said.
"The best health outcomes are achieved when a person's substance misuse is treated at the same time as their mental illness, but this requires an integrated therapeutic approach, more intensive, longer term treatment and specially trained staff."
Pitts said possible causes for the rising rate of mental illness included an overburdened public health system, sufferers attempting to self-medicate with drugs and alcohol and a greater emphasis on psychiatric assessment within treatment programs.
Odyssey's cannabis-related admissions also jumped in the last financial year to 18 per cent - up from 14 per cent in 2006-07 - while people addicted to methadone accounted for just six per cent of admissions.
The remaining five per cent of admissions were for "other" addictions to drugs including cocaine, morphine, benzodiazepine-class sedatives or buprenorphine, which can be used as an alternative to methadone.
People aged 18-30 years accounted for almost half (49 per cent) of all admissions, while 70 per cent were male.
Source: AAP NewsWire