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.
Attachment and Health
According to attachment theory people with insecure attachment have less effective strategies for dealing with negative emotions compared to people with secure attachment. One way in which insecurely individuals may try to regulate their distress is by using strategies or behaviours that are attractive for their short term relief but may have deleterious risks over years like eating, drug use or risky sex. 
In a survey of 356 primary care patients in Toronto, rates of smoking, harmful drinking and obesity, were all found to be highest in those with the most severe anxious and avoidant attachment. Both attachment anxiety and attachment avoidance have been linked in separate studies to increasing the risk of eating disorders and substance use in adolescents.