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Heightened impulsivity common in many psychiatric disorders

Results from a meta-analysis published in JAMA Psychiatry support delay discounting — a type of decision-making tied to impulsivity — as a robust transdiagnostic process across many different psychiatric disorders.

“Steeper delay discounting and, subsequently, smaller area under the discounting curve is frequently interpreted as reflecting an impulsive preference for immediate rewards over delayed gratification,” Michael Amlung, PhD, assistant professor of psychiatry and behavioral neurosciences at McMaster University, Hamilton, Ontario, Canada, and colleagues wrote. “A growing body of research has solidified the relevance of delay discounting in the context of psychiatric disorders.”

Amlung and colleagues searched online clinical databases for articles comparing monetary delay discounting between individuals with psychiatric disorders and controls using psychiatric keywords based on DSM-IV or DSM-5 diagnostic categories. However, addiction- or ADHD-related keywords were excluded to prevent redundancy with published meta-analyses.

Reward magnitudes varied from small ($0.15 to about $30) to large ($500 to $1,000) in the included studies and most used either a delay discounting task or the monetary choice questionnaire. The most common indices of discounting was hyperbolic discounting rate and area under the curve, but impulsive choice ratio and other indices were also used, according to the study.

The meta-analysis included 57 effect sizes from 43 studies across eight psychiatric diagnostic categories.

The researchers reported that all disorder categories, except anorexia nervosa, demonstrated more impulsive (ie, statistically significantly steeper) delay discounting than controls:

• major depressive disorder (Hedges g = 0.37; P = .002);
• schizophrenia (Hedges g = 0.46; P = .004);
• borderline personality disorder (Hedges g = 0.6; P < .001),
• bipolar disorder (Hedges g = 0.68; P < .001);
• bulimia nervosa (Hedges g = 0.41; P = .001);
• binge-eating disorder (Hedges g = 0.34; P = .001); and
• OCD (Hedges g = 0.3; P = .002).

Amlung and colleagues found the opposite pattern in studies of anorexia nervosa, with the psychiatric disorder group demonstrating less impulsive (ie, shallower) discounting than the control group (Hedges g = –0.3; P < .001).

Bipolar disorder and borderline personality disorder had the greatest aggregate effect sizes, and all other psychiatric disorders had small to medium effect sizes (Hedges g = 0.3 to 0.46), according to the results.

"The revelation that delay discounting is one of these transdiagnostic processes will have a significant effect on the future of psychiatric diagnosis and treatment," Amlung said in a press release. "Our results provide strong evidence for delay discounting as a core behavioral process within the [Research Domain Criteria] framework. 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." – by Savannah Demko

Disclosure: The authors report no relevant financial disclosures.