The Stages of Change Model or Trans-theoretical Model of Intentional Change (TTM) (Prochaska, 2010)  applies to many different patient groups and health conditions, it describes how people modify unhelpful behaviours, or increase or acquire helpful behaviours.

Essentially the TTM conceptualises 5 stages (see Figure 2.1 below) progressing sequentially (or as a cycle). There may be a return from a particular stage to an earlier stage, but population studies show that in personality disorder sustained recovery is more likely than relapse. Relapse can be defined as return from Action or Maintenance stage to an earlier stage. This may occur due to significant ongoing stressors or because subsequent and necessary phases of treatment have not been undertaken at an appropriate time. For example, if trauma work is not made available to an individual with post-traumatic features in a reasonable time after stabilisation, recurrence of previous unhelpful behaviours often occur. This is usually as an ineffective attempt to deal with overwhelming post traumatic symptoms.

• Pre-contemplation (Not ready) People at this stage do not intend to take action in the next six months and are often unaware of the unhelpful nature of their behaviour. Sometimes people at this stage may have tried to change a number of times with limited success and may feel demoralised and discouraged from trying again. 
• Contemplation (Getting ready) People start to recognise their behaviour is unhelpful and to look more closely at the pros and cons of their continued actions. They are usually increasingly aware of possible benefits of change but remain significantly influenced by the benefits of current behaviour and apprehensive. This balance between the pros and cons of changing can lead to people remaining at this stage for long periods of time.
• Preparation (Ready) People intend to take action in the next month or so and may begin to make small steps towards behaviour change. Action People have made specific overt modifications in reducing unhelpful behaviour and/or acquiring or increasing helpful behaviour.  
• Maintenance People maintained action for some time and are working to prevent a return to previous behavioural patterns. In this stage, change strategies are not employed as often as in the Action stage and people are typically increasingly confident that they can maintain change.

The TTM can be applied to each phase of treatment within the overall treatment pathway. For example, an individual may be in the maintenance phase with regard to stabilisation (phase 1) but in the contemplation or preparation stage with regard to trauma work (phase 2). In such a case, the TTM could help identify that the focus of the treatment should be on maintaining stabilisation and increasing motivation for trauma work.

Motivational interventions to increase intention to change can be especially useful in the precontemplation,
contemplation and preparation stages by assisting patients to reach the stage where meaningful behavioural change can occur. Examples of motivational interventions are described under Motivation in the General Treatment Strategies section.