A system includes an electronic contact lens that obtains sensor measurements from integrated motion sensors or other types of sensors and a processing module that estimates a mental state of an individual based on the sensor measurements. The processing module identifies patterns of eye movements and analyzes how these patterns change over time. Based on anatomical relationships between eye movement and mental state, the processing module estimates characteristics of the individual such as fatigue, intoxication, injury, or a medical condition that have known effects on eye movement patterns. The electronic contact lens system generates an output indicative of the estimated mental state to alert the individual to the detected condition or to initiate an automated action.