He was told he had been involved in a series of collisions with motorists, with marijuana, ecstasy and cocaine found in his system. The crisis landed him in jail, a place he never expected to be, but where he finally received a diagnosis of bipolar disorder and was given the help and medication he needed.

Matthew, 35, who asked for his last name not to be published, shared his story at the opening of Canberra's first secure mental health unit in Mugga Lane on Tuesday, where the first two patients will arrive on Wednesday - most from jail or the mental health unit at the hospital.

Matthew, who is now with the ACT Mental Health Consumer Network, said the opening of the secure unit, after a decade in the planning, was "fantastic".

In prison in 2011, he had found himself with many people who needed more focussed mental health treatment than the prison could provide.

"For those who really need assistance with quite acute and severe needs over the long term there now is a unit that's going to be able to provide that support," he said.

For mental health consumers their "self-stigma" was worse than the social stigma, he said, telling his story to encourage others to seek help. As someone from a good family and with a good education, always in work and education since age 14, he never imagined himself landing in the situation he did and never considered himself to have a mental health issue. Instead, he had self-medicated with drugs from the age of 14 and for the 16 years following.

The Mugga Lane unit has 25 beds, 10 of them in an acute wing, and most of the people there will come through the courts.

ACT Health executive director of mental health Katrina Bracher said many of the patients would have been found not guilty by reason of their mental illness, and would have the most severe of mental illnesses.

The acute section of the Dhulwa secure mental health centre would be commissioned first, with about seven patients expected by the end of the year. Once stabilised, they would move to the rehabilitation wing where they would receive 20 hours of therapy a week from pyschologists, social workers, occupational therapists, and art therapists. The unit also had an area for teaching people to cook, a gym and other facilities.

The hospital's mental health unit took people only for about two weeks at a time. Dhulwa is modelled on a two-year stay, with some expected to stay longer.

People are sent there under the Mental Health Act and by order of the Administrative and Civil Appeals Tribunal. Ms Bracher said most would come through the court system, but 10 to 15 per cent of would be sent directly from the community.

Mental Health Minister Shane Rattenbury said the location of the $43.5 million centre was fantastic, with sweeping views and the bush location providing a welcoming and peaceful environment to help people heal.

He expected 90 to 95 per cent occupation rate and the 25 beds were expected to be sufficient to meet demand, he said.

The unit will hold men and women. Each room has its own bathroom and, for privacy, the viewing glass in the door changes to opaque at the push of a button. Security is evident in the layout - with staff viewing areas behind glass, surveillance cameras everywhere but the bedrooms, moulded furniture without sharp edges, and heavy glass separating wings of the unit and covering televisions.

The United Ngunnawal Elders Council named the centre after the honeysuckle plant, for its healing properties.