Attachment and Health
John Bowlby and Mary Ainsworth developed attachment theory in the 1960s while investigating the effects of maternal separation on infant development. The development of the Strange Situation task in 1965 by Ainsworth and Wittig allowed researchers to systematically investigate the attachment system operating between children and their parents. The Strange Situation involves separating infant-parent dyads and observing infant behaviours upon reunion. Infant behaviour tended to follow patterns, leading to the development of three attachment categories: Secure, Anxious-Avoidant, and Anxious-Resistant. In 1990, Ainsworth added a new category, championed by Mary Main, called Disorganized/Disoriented attachment, characterized by its less reliable pattern of behaviour.
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.