People affected by binge eating, substance abuse and obsessive compulsive disorder all share a common pattern of decision making and similarities in brain structure, according to new research from the University of Cambridge.
The researchers reported that people affected by disorders of compulsivity have lower grey matter volumes (fewer nerve cells) in the brain regions involved in keeping track of goals and rewards.
In our daily lives, we make decisions based either on habit or aimed at achieving a specific goal. For example, if we always get lunch from the same place, we tend to follow a habitual choices or our ‘autopilot’ mode, as we know the routine well. However, if this place closes or moves, we will initially follow a ‘goal-directed’ choice to find our way to get an alternative lunch – unless we slip into autopilot and revert to walking back to the old establishment.
We cannot though always control the decision-making process, and can make repeat choices even when we know they are bad for us. In many cases this will be relatively benign, such as being tempted by a cake whilst slimming, but in extreme cases it can lead to disorders of compulsivity.
In order to understand what happens when our decision-making processes malfunction, the Cambridge researchers compared around 150 individuals with disorders including methamphetamine dependence, obesity with binge eating and obsessive compulsive disorder, with healthy volunteers of the same age and gender.
Participants initially undertook a computerised task to test their ability to make choices aimed at receiving a reward, over and above making compulsive habitual choices. The results suggested that the disorders were connected by a shift away from goal-directed behaviours towards automatic choices. In a second study, brain scans in healthy individuals were compared with a subset of obese individuals with or without binge eating disorder. The scans showed that obese subjects with binge eating disorder have a lower grey matter in the orbitofrontal cortex, the brain region involved in keeping track of goals and rewards compared to those who do not binge eat.
The researchers concluded that seemingly diverse choices – drug taking, binge eating despite being overweight, and compulsive cleaning or checking – have an underlying common thread: rather than a person making a choice based on what they think will happen, their choice is automatic or habitual.
Compulsive disorders can have a profoundly disabling effect on individuals. Research like that undertaken at Cambridge allows an insight into what can go wrong in decision making, and may suggest developing treatments focused on forward planning or interventions which target the shift towards habitual choices.