Impulsivity Found in a Wide Range of Psychiatric Disorders
The tendency to choose smaller immediate rewards over larger delayed rewards can be found in a broad range of psychiatric disorders, according to a new Canadian study published in the journal JAMA Psychiatry.
Previous research has linked a greater preference for immediate rewards and impulsivity to negative health outcomes, such as addiction, obesity and attention-deficit/hyperactivity disorder (ADHD).
The new study reinforces this association, finding that this type of impulsive decision-making, called delay discounting, is consistently observed across an even broader range of psychiatric disorders, including bipolar disorder, schizophrenia and borderline personality disorder.
“The revelation that delay discounting is one of these ‘trans-diagnostic’ processes will have a significant effect on the future of psychiatric diagnosis and treatment,” said lead author Michael Amlung, assistant professor of psychiatry and behavioral neurosciences at McMaster University in Ontario and researcher for the Peter Boris Centre for Addictions Research at St. Joseph’s Healthcare Hamilton.
For the analysis, the research team observed data from 40 different studies looking at several different psychiatric disorders: major depressive disorder, bipolar disorder, borderline personality disorder, schizophrenia, eating disorders, and others.
The largest delay discounting effects were found in bipolar disorder, borderline personality disorder and schizophrenia.
Interestingly, the findings show the opposite pattern in those with anorexia nervosa. The researchers explained that the greater preference for delayed over immediate rewards seen in anorexia patients is consistent with excessive self-control of their eating habits.
The study authors say this pattern suggests that delay discounting preferences are best thought of as being on a continuum, with some disorders exhibiting excessively impulsive decisions and other disorders exhibiting excessively self-controlled decisions.
“Examining factors that cut across psychiatric disorders, such as delay discounting, helps to illuminate commonalities and distinguishing characteristics amongst disorders that then guide further research on treatment and prevention,” said Randi McCabe, co-author of the paper, psychologist-in-chief at St. Joseph’s Healthcare Hamilton and professor of psychiatry and behavioral neurosciences at McMaster.
“The more we understand the nature of psychiatric illness, the better we are equipped to provide effective treatment strategies,” she said.
The authors say the study findings support the inclusion of delay discounting in the Research Domain Criteria (RDoC) framework proposed by the National Institute of Mental Health, as a potent indicator of psychiatric illness. RDoC is a biologically-valid framework for understanding mental disorders and includes research approaches in genetics, neuroscience and behavioral science.
“Our results provide strong evidence for delay discounting as a core behavioural process within the RDoC framework,” Amlung said. “On a broader level, this study underscores the need for future research examining common neurobiological and genetic underpinnings of this type of decision making in order to inform evidence-based treatments across psychiatric disorders.”
Source: McMaster University