Adolescence is a period in individual development of rapid neurological, psychological and biological change. This period is often delimited by the teenage years, although some consider adolescence to continue until the age of 25. During this highly complex period of personality development dramatic changes take place in the adolescent's expectations, in the values and beliefs of his family and in his outside world. This results in an individual with increased reliance upon peer groups rather than the family of origin and one who is capable of a separate existence in the world.