Developmental psychology
Attachment theory, originally developed by John Bowlby, focuses on the importance of open, intimate, emotionally meaningful relationships. Attachment is described as a biological system or powerful survival impulse that evolved to ensure the survival of the infant. A child who is threatened or stressed will move toward caregivers who create a sense of physical, emotional and psychological safety for the individual. Attachment feeds on body contact and familiarity. Later Mary Ainsworth developed the Strange Situation protocol and the concept of the secure base.
Yukio Ishizuka
In 1976, while many psychiatrists continued to be preoccupied with the definition of psychological illnesses (Diagnostic Statistical Manuals), Ishizuka turned to a monograph by M. Jahoda published in 1958 entitled « Current Concepts of Positive Mental Health.» Jahoda offered six conditions for developing and evaluating future models of Positive Mental Health. In doing so, she pointed out the limits of the ‘disease’ model and set guidelines to define models of health applicable both in wellness and disease. 
Concluding that the ‘medical’ or ‘disease model’ used in psychiatry was not fit to understand healthy human beings or to assist them in ‘normal’ or optimal functioning, Ishizuka began to build such a model. His exposure to the East, and training in the West helped him develop a model of health across different cultures. Focusing almost entirely on the experience of his diverse patients, he challenged what he knew to define a model of health and personality applicable both in extreme distress and optimal health.