The young man, whom CBC News has chosen not to name, has mood swings and behavioural issues, including violent outbursts.
He has been unable to remain in a group home and last Sunday, he checked himself out of the long-term mental health facility Centracare, wearing only a Johnny shirt in the subzero temperatures.
"I feel that he is in danger. I feel that his safety is in danger," said the young man's father.
Although there are facilities in other provinces and in Maine that are equipped to deal with such cases, none currently exist in New Brunswick, he said.
'He needs the housing, but he also needs the help and he's not getting that. He's not getting that at all.' —Father
Instead, the young man has been bounced around between group homes, hospitals and the courts most of his life while the province tries to find a place for him to live.
"I can't get answers," said his father.
"The only answer I get is basically 'Why can't he come back and live with you?' and I love my son, but I'm unable to provide the help that he needs.
"He needs the housing, but he also needs the help and he's not getting that. He's not getting that at all."
The young man had been living at Centracare since October and his father says he was told the province would find him a place to stay by December.
"That hasn't happened and every time there's a conference call to discuss the plan, it’s the same thing over and over and over — they're looking, but they can't find a place," his father said.
"It's about time somebody tried to find something for my son and…I would appeal to the premier to get involved with this because this has been something that has been going on since my child was six, seven years old. It's not new, he's 18 and it's very stressful on him, it's very stressful on us as his parents and something needs to be done before something happens to my son."
Centre of excellence recommended in 2008
He contends the provincial government needs to follow through on a recommendation by the province's former child and youth advocate that dates back to 2008 and create a centre of excellence for children and youth facing similar issues.
"I've been told for my son if nothing comes to light then basically he would be put up in a hotel with 24-hour supervision. That's not care, that's housing a child with someone that, with all due respect to the person that may be looking after him, it's a babysitting service and they're not addressing the problem here at all. They're just Band-Aiding it," he said.
"It's not right to have children, or adults for that matter, with these disabilities that can't get the help in this province.
"At a time when they are talking about cutting back the Department (of Social Development) in terms of funding, I think they should be putting more funding into it."
Bernard Richard, the province's former child and youth advocate, said he believes the provincial government has recognized there is a problem.
"I've been generally encouraged," he told CBC on Wednesday.
"They are feeling that they need to do something and I am hopeful that they will."
In 2008, in his report called Connecting the Dots, Richard recommended a centre of excellence be dedicated to research and the provision of services to children with very complex needs, including the establishment of community-based residential capacity for them.
The centre was one of 48 recommendations in the report, which was a two-year undertaking and included a review of seven individual complaint files relating to youth with very complex needs.
Richard called for a centre of excellence again last year in report called Staying Connected, which he co-authored as co-chair of a task force on a centre of excellence for children and youth for complex needs.
"When a placement outside of the home is required for assessment or step-up intervention purposes, the centre of excellence will help ensure that clinicians, educators, social workers and all interveners work together and from the same page in meeting the child’s needs," the report said.
"The millions expended to date for step-up interventions abroad could benefit many more children if they were spent here in New Brunswick; those expenditures could develop expertise, services and employment in communities around our province."
The province has sent young people to a facility in Maine for care in the past.
A spokesperson for the Department of Social Development could not say if young people are still being sent out of province for such care.