It is generally accepted that there are three main attachment styles in adults and children - secure, ambivalent and avoidant. (Bower 1997,a). A national survey of representative samples of 8,080 U.S. adults between 15 and 54 years of age (Bower, 1997, b) by Mickelson, Kessler and Davis, nearly all of the participants were found to conform to one of the three attachment groups.
The survey concluded that attachment patterns are the central developmental factor responsible for subsequent personality and social development. While secure attachments, seen in about 59% of those surveyed, led to stable lasting relationships in later life, the 29 % displaying avoidance later developed fear or apathy towards emotional intimacy. Manipulative, distrustful behavior towards romantic partners was a feature of the remaining 11% or so, displaying ambivalent (or anxious) behavior. Finally, the study also pointed out the close association between insecure attachments in childhood and the occurrence of physical abuse or neglect, both of which can contribute to the development of mental illnesses.
John Bowlby, the father of attachment theory, considered attachment as a biological necessity - he noted separation anxiety of young children and how babies needed to cling to their mothers in times of stress.