There has been recent debate in the literature regarding how to adequately measure and define habitual behaviour [1, 2]. On one hand, habit is argued to be automatic and lacking in awareness, intentionality or controllability while being generated by certain cues in the environment. On the other hand, habit is thought to occur through repetition as opposed to other automatic behaviours that may be prompted by implementation intentions or reflexes.

A part of the problem in defining habitual behaviour is that measurement is often centred around health behaviours that while repeated can have subtle differences in their action. For example, in the case of the habitual behaviour of consuming convenient yet unhealthy fast food, the ‘habit’ of eating could be considered repetitive but the context surrounding the habit may change. It is argued that sleep-related behaviour presents an interesting avenue for understanding true habitual behaviour in that the context leading up to sleep (i.e. the home environment) in which the behaviour occurs in is often very similar. Moreover, whereas many health behaviours also constitute a singular behaviour, sleep-related behaviours constitue a multitude of actions each showing stronger or lessening degrees of automaticity. Finally, the very nature of sleep-related behaviour is that the closer one gets to the final point of action (i.e. sleeping), the lower the level of awareness and so the higher the likelihood that the behaviour could be considered ‘automatic’.

Surprisingly, sleep-related behaviour as a habit remains relatively understudied in the behavioural medicine context. One reason for this is that sleep-related behaviours often fall right along the dimension of habitual versus non-habitual behaviours depending on their nature and proximity to going to sleep itself. There is also a lack of understanding on which sleep-related behaviours are most likely to contribute to sleep quality. An interesting line of research to pursue is to assess whether behaviours that disrupt the sleeping process are more or less likely to be considered habitual. Research could also generate some behaviour-specific measures of habit. For example, recently, the Sleep–Hygiene Index was tested as to the habitual strength of each behaviour (using the self-report habit index) [3]. Rather than using two measures to test habit strength though, it may be worth trying to encapsulate all the factors within a singular scale. This measure could then be translated to the measurement of habit strength of other specific health behaviours. Given the questions on habit, take note of the very elements that are considered central to sleep-related behaviour; it is recommended that more research is done in this area to ensure that these avenues are properly explored.