Many accounts of health behaviours and behaviour change draw upon the centrality of individual characteristics; including, for instance, self-efficacy. Self-efficacy relates to ......... It comprises four distinguishable factors, including  enactive attainment, vicarious experience, social persuasion and physiological factors. Self-efficacy is an element which is touched upon in many theories of behaviour change; including that of the TPB (Azjen, 1991) in relation to perceived behavioural control, and in the TTP whereby self-efficacy is a central denominator of behaviour change stages (Prochaska et al., 1992). Self-efficacy is even presented as a predictor, mediator or moderator of behaviour change; as proposed in Bandura’s Social Cognitive Theory (1997). Self-efficacy both directly and indirectly impacts health through decision making, including behaviours such as smoking, physical exercise, dieting, condom use, dental hygiene, seat belt use, and breast examination (Conner, 2005). In all, research consistently demonstrates that positive behaviour change is more likely to occur if an individual has a high level of self-efficacy REF. Moreover, high levels of self-efficacy increase task-motivation and the longevity of a behaviour REF.  Targeting the four factors of self-efficacy can increase the likelihood of behaviour change (Ashford, Edmunds & French, 2010). 
The above literature is a small focus amongst a larger area of work surrounding behaviour change. Other theories provide additional standpoints, including the Theory of Interpersonal Behaviour which highlights the importance of habit formation (Triandis, 1977; 1980), the Theory of Trying which focuses on the influencers upon the intention to try (Bagozzi, 1992), and the Self-determination Theory which focuses on innate psychological needs for competence, autonomy and relatedness (Deci & Ryan, 1985; Ryan & Deci, 2000).
Enduring behaviour change may also be achieved by understanding an individuals past experiences and habitual tendencies.  Habits may be formed through repetition of a behaviour within a specific context (Lally, van Jaarsaveld, Potts & Wardle, 2010). Eventually, this context will have the potential to trigger the behaviour without awareness, conscious control cognitive effort or deliberation (Bargh, 1994; Lally, van Jaarsveld, Potts, & Wardle, 2010; Wood & Neal, 2009).The development of positive health behaviours have been demonstrated relating to diet (Adriaanse et al., 2010), physical activity (Rhodes & de Bruijn, 2010), alcohol consumption (Norman, 2011) and medication adherence \citep*{Bolman2011}.
When devising interventions to build habitual behaviours, it is important to consider the context in which an intervention is applied. For example, when aiming to ameliorate unhealthy behaviours, disrupting a cue exposure which triggers the behaviour could be a focus (Verplanken, Walker, Davis & Jurasek, 2008), however, there is the possibility of the behaviour returning when the necessary cue or context returns. This serves as an explanation as to why positive results from interventions may be short-lasting. Judah and colleagues (2018) aimed to investigate the formation of habits to create positive health behaviour changes. In line with the above discussion, they found that performing a behaviour in a more stable context was associated with more frequent repetition, which they attributed to context-specific cues being effective reminders. They also reported behaviour pleasure and intrinsic motivation to be two key factors in predicting whether a behaviour becomes a habit. Conversely, they found perceived utility and behaviour benefits to have no impact on habit formation, contradicting the HBM which highlights a key focus on perceived threat of behaviour to one’s health. Previous behaviours and habit formations are important factors when devising intervention strategies for individuals, as these behaviours have ingrained neural pathways that are easily activated (Gerdeman, Partridge, Lupica, & Lovinger, 2003; Smith, 2016; Yin & Knowlton, 2006). For this reason, strategies need to be employed that will both combat the old health behaviour and encourage the formation of neural pathways associated with the new health behaviour.
CONTEXT - In complex interventions, effects are produced not only by the intervention, but are strongly linked to context. 10.1080/08870446.2014.953530