By Liver, Spleen, Kidney, and others

Those that caused by liver system, there are two main mechanisms: 

1. Deficiency of liver-yin or kidney-yin that cannot counteract the hyperactivity of liver-yang.
2. Emotional disturbances such as anger or grief cause liver to lose control of its qi. The stagnated qi stays trapped and turned into fire, burning off liver-yin as time goes by. Once liver-yin loses out liver-yang will take over and the phenomena of adverse of liver-qi will be observed.

Those that caused by spleen system can be due to inappropriateness in eating, imbalance in working and rest, malfunction of spleen. The formation of pathogenic damp-phlegm in reality intercepts the clear yang energy from floating up and clouded yin from descending. Again, clear openings are blocked; brain loses the nourishment from clear yang, qi, blood. Headache takes place. 

Those that caused by kidney system, the causes can be genetically insufficiency, lacking of kidney essence, overwork or over-desire, over sexual activities, exhaustion of kidney-yin. These all contribute to mal-nourishment of channels leading to brain and brain stem and thus cause headache.

Others such as physical accidents and bed-ridden patients with prolonged illnesses may have stagnancy of both blood and qi.