They also used a recognised depression measurement scale to assess people, and carried out an emotion recognition computer test, - where people are asked to respond rapidly to happy or sad words.
Based on her scores in February from a widely used psychological test called the Hamilton Rating Scale for Depression, Guyton's mental illness is in remission.
The research teams looked at almost 4, 500 elderly people and, during a 90 minute home interview, graded their level of depression using the same scale, giving them points for every depressive symptom.
One told me that being involved in Crossrail was like his own Hoover Dam (the huge US dam built during the Great Depression) in terms of scale and personal achievement.