Obsessions and compulsions are the hallmarks of obsessive-compulsive disorder (OCD). In the dominating cognitive model, compulsions are voluntary actions performed to reduce the likelihood that an unwanted, or feared, consequence will take place. Neuroscientists are now challenging this view with a competing explanation where obsessions arise from compulsions, not the other way around.

Efficient habits and flexible goals

What are the forces driving our behaviour? Habits and goal-directed behaviour compete for control over how you behave. Habits are fast and efficient but rigid and inflexible. Goal-directed behaviour, on the other hand, is flexible but takes effort. Both have their advantages and we want a mix of them, not letting one rule out the other.

In OCD, there is a shift in this balance toward habitual behaviour. Individuals with OCD have a higher tendency to develop habits and rely on habits in more situations, making their behaviour automatic and inflexible. They continue to respond in a way that has been previously rewarded, even though the reward is no longer present. Most individuals with OCD understand that their behaviour is exaggerated and illogical, but find it hard to control. In this way, compulsive behaviour can be seen as a form of habits rather than goal-directed behaviour.

“…both habits and compulsions continue in spite of awareness that these actions are not useful/wanted (i.e., ego-dystonic) and are associated with the experience of an urge to perform them” Gillan et al., 2015

Habitual and goal-directed behaviour activate different networks in the brain, and OCD has been linked to over-activity in the network for habits and under-activity in the network involved in goal-directed behaviour. Experiments on rodents have shown that activating the habitual network increases compulsive behaviour, pointing to a link between habits and compulsions in terms of brain activity.

What about obsessions? Proponents of this “habitual theory of OCD” view obsessions as something we construct to make sense of compulsions, which is in contrast to cognitive theories of OCD where compulsions are seen as voluntary behaviour performed with the goal of reducing anxiety or preventing an undesired outcome.

Indeed, it is impossible to ignore the tight coupling between the content of obsessions and compulsions in OCD, which leads to the intuitive inference: “I fear contamination and therefore I feel compelled to clean excessively”. Based on recent observations, we propose that the reverse - “I feel compelled to clean excessively and therefore I must be afraid of contamination” - may better capture the OCD phenomenon. Gillan & Robbins, 2014


The habitual theory of OCD flips the cause/effect direction between obsessions and compulsions to propose that compulsions arise from excessive habit formation and obsessions are our way to explain the compulsive behaviour. I think it’s an interesting theory with a strong foundation in neuroscience that has not yet resulted in improved treatment of OCD. A better understanding of the brain networks involved in OCD will hopefully help us to tailor treatment so that each individual with OCD is given the best possible chances to recover.