Post-quake stress, insurance woes, relationship issues and service cuts have combined and now people "just can't deal with it anymore", said Mental Health Advocacy and Peer Support (MHAPS) manager Sue Ricketts.
"The multiplicity of crises people are experiencing over time, particularly for young people, is causing massive problems for mental health."
MHAPS is a non-governmental organisation that provides services for people suffering with mental health issues and addictions.
It was experiencing high need with around five to seven new clients walking through its doors every week in October-November last year, but that has now doubled to 10-15.
Post-quake CDHB figures show an increase of 79 per cent in new child and youth cases, and 30 per cent in children and youth under monthly care.
It has also seen a 95 per cent increase in new rural cases and 40 per cent increase in adult contacts.
New adult contacts number 22,277 post-quake - which is 530 more adults seeking medical help through the CDHB every month.
The increase in people with mental health problems was predicted following a pattern to previous natural disasters, CDHB planning and funding team leader Greg Hamilton said.
"Despite many positive changes to services, this system remains under pressure. After five years both the mental health and general health workforces are showing signs of strain in their efforts to provide the best possible service to our population."
While national District Health Board targets aim for 80 per cent of youth mental health patients to be seen within three weeks, in Canterbury it was 71.5 per cent.
Another 24.1 per cent were seen within three to eight weeks, and 4.4 per cent had to wait eight weeks or more.
Long waiting lists could cause some serious long-term issues, Mrs Ricketts said.
"We had to close our own waiting list at one point because it got too long, but I'm worried especially with the young people that if they fall through the cracks now, we'll be seeing some much more serious problems down the track."
She added that the workloads and stress are "incredibly hard" on staff, who are often dealing with their own issues post-quake.
"They need help too."