For definitions of attachment styles, behaviours and other concepts click on Attachment Definitions

Following Bowlby, we assume that attachment is an essential facet of human development and that a key function of the family is to provide a framework for the development of increasingly autonomous personality functioning, underpinned by a secure attachment system.

Families in which serious psychiatric crises arise in adolescence tend to have distortions of the attachment system. This may be a result of chronic disturbance in a specific individual, or the parental relationship; additionally it may reflect the behaviour of a caregiver in the past, the intense pressures placed on the caregiver by the child earlier in development, or most commonly both of these.

In some key respect, the family has ceased to be a Secure Base, in that either the YP does not feel reassured by the presence of other family members, or those family members have ceased to be able to offer support and acceptance, thus the attachment system does not function to contain the YP's disturbed emotional states or behaviour.

Within our framework, the capacity of the family to have a sufficiently coherent picture of each others' states of mind is a key facet of attachment (see Mentalization). One sign of the disturbance in the attachment system is that there are massive distortions of perceptions of other people's attitudes and intentions, and that an aim of the intervention is to reinforce attachment processes through enhanced understanding.

The moment of crisis may be understood as a breakdown of the attachment system, in which the parents and/or the YP are willing to give up the bond that would normally make the troubled YP seek security and safety in the family. This may be a reaction to a long history of dismissing attachment style, or preoccupied entanglement, or the dramatic exaggeration of a developmentally appropriate move away from the family. Whatever the roots may be, the aim of the crisis intervention is to make the family a more secure base for the YP. What may be most important in that context is that the keyworker (KW), through his intensive and reassuring presence, begins this experience for the family members of a more secure base. The calm, sensitive, appropriate behaviour of the KW is intended to activate more secure Internal Working Models of attachment relationships for all members of the family.