What is it with these OCD people? They clean their hands, many times in a row. They click switches on and off, over and over. They check — and re-check, and check again — that they turned the stove off.
Why does it happen? No one really knows just what drives people with obsessive-compulsive disorder to do what they do, even when they’re fully aware that they shouldn’t do it, and when it interferes with their ability to live a normal life.
Story continues after video.
That lack of scientific understanding means about half of them can’t find an effective treatment.
But a new analysis of brain scans from hundreds of people with OCD, and people without the condition, may help. Larger than any previous study, it pinpoints the specific brain areas and processes linked to those repetitive behaviors.
Put simply, the study suggests that the brains of OCD patients get stuck in a loop of “wrongness”, that patients can’t stop even if they know they should.
Researchers from the University of Michigan gathered together the largest-ever pool of task-based functional brain scans and other data from OCD studies around the world, and combined them for a new meta-analysis published in Biological Psychiatry.
Credit: University of Michigan
Ignores stop signals
“These results show that, in OCD, the brain responds too much to errors, and too little to stop signals, abnormalities that researchers had suspected to play a crucial role in OCD, but that had not been conclusively shown due to small numbers of participants in the individual studies,” says Luke Norman, Ph.D., lead author of the new study and a postdoctoral research fellow in the U-M Department of Psychiatry.
“By combining data from ten studies, and nearly 500 patients and healthy volunteers, we could see how brain circuits long hypothesized to be crucial to OCD are indeed involved in the disorder,” he says. “This shows the power of doing this kind of research more collaboratively.”
The analysis helps set the stage for new therapy targets, said U-M psychiatry faculty members Kate Fitzgerald, M.D. and Stephan Taylor, M.D. Fitzgerald leads a clinical trial that is currently seeking teens and adults with OCD to test the ability of targeted therapy sessions to treat OCD symptoms.
“This analysis sets the stage for therapy targets in OCD, because it shows that error processing and inhibitory control are both important processes that are altered in people with the condition,” said Fitzgerald.
“We know that patients often have insight into their behaviors, and can detect that they’re doing something that doesn’t need to be done,” she adds. “But these results show that the error signal probably isn’t reaching the brain network that needs to be engaged in order for them to stop doing it.”
In their paper, the researchers focus on brain areas linked by highways of nerve connections deep in the center of the brain. They normally act as a monitor for errors or the potential need to stop an action.
The pooled brain scan data used in the new paper was collected when OCD patients and healthy people were asked to perform certain tasks while lying in a powerful functional MRI scanner. In all, the new analysis included scans and data from 484 children and adults, both medicated and not.
Norman led the combining of the data in a carefully controlled way that allowed for the inclusion of brain scan data from studies conducted as far apart as the Netherlands, the United States and Australia.
It’s the first time a large-scale analysis has included data about brain scans performed when participants with OCD had to respond to errors during a brain scan, and when they had to stop themselves from taking an action.
A consistent pattern emerged from the combined data: Compared with healthy volunteers, people with OCD had far more activity in the specific brain areas involved in recognizing that they were making an error, but less activity in the areas that could help them stop.
The researchers recognize that these differences alone aren’t the full story — and they can’t tell from the available data if the differences in activity are the cause, or the result, of having OCD.
But they suggest that OCD patients may have an “inefficient” linkage between the brain system that links their ability to recognize errors and the system that governs their ability to do something about those errors. That could lead their over-reaction to errors to overwhelm their under-powered ability to tell themselves to stop.
“It’s like their foot is on the brake telling them to stop, but the brake isn’t attached to the part of the wheel that can actually stop them,” Fitzgerald says. “In cognitive behavioral therapy sessions for OCD, we work to help patients identify, confront and resist their compulsions, to increase communication between the ‘brake’ and the wheels, until the wheels actually stop. But it only works in about half of patients. Through findings like these, we hope we can make CBT more effective, or guide new treatments.”