Exercise may also result in detrimental changes in mental health. Some individuals can become overly dependent on physical activity and exercise to an excessive degree. This abuse of exercise can result in disturbances in mood and worsened physical health. In the case of athletes the intense training, or overtraining, necessary for endurance sports consistently results in increased mood disturbance. Extreme cases of overtraining may result in the staleness syndrome; a condition associated with deteriorating performance and behavioural disturbances including clinical depression