The California Workers' Compensation Institute (CWCI) published a new study on cumulative trauma (CT) claims, reviewing claim trends from 2018-2025, utilizing their Industry Research Information System (IRIS).

CT claims nearly doubled as a share of California workers’ comp claims during the study period, going from 9.1% to 16.5%, with most of the growth occurring after 2021.

Researchers concluded that the increase cannot be fully explained by traditional factors, as CT rates increased across every region, industry, body-part category, and worker tenure group, including regions where CT claims historically were less common. These findings suggest that broader changes may be contributing to the increase in CT claims.

Approximately 87% of CT claim growth resulted from more workers filing CT claims, rather than an increase in multiple filings by the same worker.

The largest increases in CT claims occurred in soft tissue, mental disorder, and other facial soft tissue claims, with mental disorder claims emerging as a significant contributor to CT growth.

Southern California law firms represented 23% of CT cases involving Northern California employers in 2019, compared with 79% in 2025. During the same period, Northern California CT cases filed in Southern California venues increased from 15% to 38%.