California Self‑Insurance Plans (SIP) Exam 2026 - Free SIP Practice Questions and Study Guide

In psychiatric injury cases, causation isn’t about the work factor being the sole cause, but about it contributing in a meaningful, substantial way. The substantial-cause threshold means the workplace event must be a material contributor to the injury, not a minor or remote influence. The commonly used range to illustrate this threshold is roughly 35-40%, meaning the work factor needs to account for a substantial portion of the risk—not just a negligible amount, but it doesn’t have to be the single majority cause.

This recognizes that psychiatric injuries often arise from multiple factors, including preexisting conditions, personal stressors, and workplace events. If the workplace factor contributes around a third to two-fifths of the total risk, it meets the threshold; contributions far below that would likely be considered insufficient, while requiring it to be the majority cause (50% or more) is unnecessarily strict for a “substantial” contributor in this context.