Insomnia can be caused by stagnation of various substances, such as qi, blood, food, or phlegm. Each type of stagnation creates a different pattern of insomnia, and it is crucial to differentiate these patterns before trying any treatment. Qi stagnation in the Heart can be correlated with reduced circulation in the chest, and often results from shock or trauma. Blood stagnation, a more localized obstruction, can present as coronary artery disease. If there is stagnation of food in the digestive system the parasympathetic nervous system can be under-activated. Insomnia that presents with other mental health issues is considered to be phlegm, or mucus, that is obscuring the Heart and effecting consciousness. The phlegm often comes from the digestive system, and there is a link between digestive function and mental health issues.