Thousands of Kaiser Permanente mental health professionals throughout California started a weeklong strike Monday to protest what they say is a lack of staffing that affects care.

Outside Kaiser Permanente hospitals and clinics in the San Francisco Bay Area, dozens of workers marched Monday holding signs that said: "Kaiser, Don't Deny My Patients Mental Health Care," and "Care Delayed is Care Denied."

About 4,000 psychologists, therapists, social workers, psychiatric nurses and other medical professionals represented by the National Union of Healthcare Workers say they will picket through Friday.

Some non-urgent mental health and other appointments may need to be rescheduled but anyone in need of urgent mental health or other health care will receive the services they need, said Elita Fielder, a spokeswoman for Kaiser Permanente.

"They've canceled appointments for these five days, but there's a critical situation every day of the year," Sal Rosselli, National Union of Healthcare Workers president, told the East Bay Times.