More than 2,400 Kaiser Permanente psychologists, therapists, social workers and other mental health workers in Southern California began an open-ended strike Monday over increased workloads and staffing shortages that their union said have created a “substandard” system of care.

The National Union of Healthcare Workers said nearly 2,400 mental health workers launched the job action after Kaiser Permanente management turned down their proposals.

Thousands of Kaiser Permanente mental health workers have gone on strike in Southern California, saying they're overworked and lack crucial benefits. Meanwhile, the company has said the union is dragging out negotiations and it has already taken major strides to improve labor conditions.