A new study finds people with compulsion disorders such as substance abuse, binge eating and obsessive compulsive disorder have similar patterns of decision making and brain structures.
Reporting their findings in the journal Molecular Psychiatry, the researchers explain how they discovered people affected by disorders of compulsivity tend towards automatic habitual choices than goal-directed behaviors. Plus, they also have lower grey matter volumes - which indicates fewer brain cells - in brain regions that help track goals and rewards.
First author Dr. Valerie Voon, honorary consultant neuropsychiatrist and Wellcome Trust Fellow with the Department of Psychiatry at the University of Cambridge in the UK, says:
"Seemingly diverse choices - drug taking, eating quickly despite weight gain, and compulsive cleaning or checking - have an underlying common thread: rather that a person making a choice based on what they think will happen, their choice is automatic or habitual."
Everyday decisions are either habitual or goal-oriented
Every day we make decisions, and these tend to be of two types: habitual or goal-oriented. A good example of habitual decision-making is when we are on "autopilot" as we drive the familiar route home from work. This can slip into goal-oriented behavior if we are diverted onto a less familiar road - the goal being to get back to the familiar route.
MRI results showed that the obese participants with binge eating disorder had lower grey matter volumes than other study participants.
Sometimes we struggle to control our decision-making: we end up in the habitual stream even though we want to be in the goal-oriented stream. Take, for example, jumping into the car to nip to the shops, when we have vowed to walk more, or having that extra piece of cake when we are supposed to be watching our weight. These are fairly benign examples of compulsive behavior. Disorders of compulsivity arise when these behaviors become extreme.
To understand what happens when our decision-making goes wrong in this way, the Cambridge team compared nearly 150 people with compulsion disorders - including obesity with binge eating, methamphetamine dependence and obsessive compulsive disorder - with healthy individuals matched by age and gender.
First, the participants carried out computer tasks that tested their ability to make goal-oriented choices aimed at getting rewards versus compulsive choices.
Then the researchers compared MRI brain scans of three groups of participants: a subset of obese individuals with and without binge eating disorder, and healthy volunteers. Binge eating is a compulsion disorder where the affected person devours vast amounts of food very quickly.
Compulsion disorders more closely linked to habitual choices, less grey matter
The results showed there was a common decision-making pattern in the groups with the compulsion disorders: they all showed a shift toward automatic habitual choices and away from goal-oriented behaviors.
The MRI results showed that compared to the healthy volunteers and counterparts who did not binge eat, the obese participants with binge eating disorder had lower grey matter volumes - indicative of fewer neurons or brain cells - in the orbitofrontal cortex and striatum of the brain. These brain regions help keep track of goals and rewards.
Plus, the researchers noticed how even among the healthy volunteers, those who tended to make more habitual choices in the first part of the study also tended to have lower grey matter volumes in those brain regions.
"Compulsive disorders can have a profoundly disabling effect on individuals," says Dr. Voon, noting that:
"Now that we know what is going wrong with their decision making, we can look at developing treatments, for example, using psychotherapy focused on forward planning or interventions such as medication that targets the shift towards habitual choices."
The study follows two earlier Cambridge papers published in Biological Psychiatry that describe how researchers - including some who worked on this latest study - found a propensity for bad habit formation in obsessive-compulsive disorder (OCD). They identified a model of compulsivity that may extend beyond OCD and prove to be a good indicator of how people more generally lose control over their behavior.
Written by Catharine Paddock PhD