Mental health clinicians for Kaiser Permanente have authorized a five-day strike, with approximately 4,000 caregivers across California expected to participate.

According to a press statement released by the National Union of Healthcare Workers (NUHW), the strike is in regards to an ongoing problem with understaffing.

The release added that the workers’ three-year contract (which expired in September) included provisions intended to increase staffing and reduce patients’ wait times for follow-up appointments. However, understaffing and lengthy delays have reportedly persisted, forcing patients to pay out of pocket for non-Kaiser therapists, or go without treatment.

“This ultimately comes down to resources,” said Sal Rosselli, NUHW president. “Kaiser has $42 billion in cash and investments, but it underfunds its mental health care services to the point that overworked clinicians are leaving in droves and patients with serious conditions wait weeks for appointments or are pushed into group therapy.”

A 2011 complaint filed by Kaiser clinicians resulted in California’s Department of Managed Health Care, issuing a $4 million fine against Kaiser in 2013 for violating the state’s Mental Health Parity Act and timely access rules.

John Nelson, vice president of communications for Kaiser Permanente, said that in the past three years, these issues have been vastly improved.

“We acknowledge that this has not been easy and that we have more to do,” Nelson said. “We have increased the number of therapists on staff by 30 percent since 2015 and continue to aggressively hire more, despite the nationwide shortage of professionals.”

Nelson also criticized the NUHW for threatening to call a strike during the holiday season. The strike is authorized to begin next month unless an agreement can be reached on a new contract.