My friend gets very angry, very severe headache, difficulty in sleep and starts hurting himself when he gets angry. he also has stress.

See Professional: Anger is superficial emotion and there are always stories/ emotions underneath anger. Professional can help him to deal with stress and anger. Some people hurt because they get hormone release in the body which works as pain killer for them and make them feel good. Please go for counsellor or psychologist. Ask friend to develop healthy day routine if possible. best of luck.