Adults with insecure attachments and patterns of unhealthy relationships develop these because of poor early childhood experiences. When parents are not able to respond to their infants in empathic and consistent patterns, such infants over time come to believe that such patterns are the basis of all human interactions. Such beliefs are deeply imbedded in the brain's structure and may operate at an unconscious level and influence the infant for the rest of their lives.

Some reasons for such poor early experiences may be:

• The attachment pattern of the parent
• A traumatic event impacting on the parent so they are not emotionally available
• The death of a parent
• A long standing parent illness
• Early separation from the primary parent, because of the infants’ illness and hospitalization
• Marital separation/divorce resulting in long absences from one parent or both at an early age
• Severe parental stress due to poverty, poor housing, marital conflict, cultural norms, etc.
• Child abandonment

If the child does not have other adults in their life to act as a secure attachment base, the child will continue to present the difficult attachment behaviors developed as an infant or young child into older childhood and adolescence. Peers and adults involved with the child may respond in negative ways to the child’s behavior, thus confirming for the child that others are not to be trusted and that they do not deserve positive experiences. Such beliefs and patterns of behavior will continue into adulthood, more rigidly internalized and outside the person’s awareness.