Delay discounting occurs across psychiatric diagnoses and may represent an important target for interventions, according to meta-analysis results published in JAMA Psychiatry.

Delay discounting describes the extent to which rewards lose their value with a temporal delay. Steeper delay discounting reflects greater impulsivity and a preference for immediate gratification over delayed rewards.

Researchers sought to determine whether excessive delay discounting is exhibited across psychiatric diagnoses. Michael Amlung, PhD, of the Peter Boris Centre for Addictions Research, St Joseph’s Healthcare Hamilton and the Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada, and colleagues conducted a meta-analysis of the published literature on delay discounting in people with psychiatric illness. They computed Hedges g effect sizes and used random-effects models for all analyses. The main outcome was categorical comparisons of delay discounting between a psychiatric group and a control group.

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Researchers reported that the greatest aggregate effect sizes were observed for bipolar disorder (Hedges g, 0.68) and borderline personality disorder (Hedges g, 0.60), whereas small- to medium-sized effects were found for other psychiatric disorders, including bulimia nervosa (Hedges g, 0.41), binge-eating disorder (Hedges g, 0.34), major depressive disorder (Hedges g, 0.37), and schizophrenia (Hedges g, 0.46). In contrast, anorexia nervosa exhibited significantly shallower delay discounting, with a Hedges g effect of −0.30.  

The researchers noted that delay discounting appears to exist along a continuum, which is illustrated by the results for eating disorders. Whereas bulimia nervosa and binge eating exhibit steep delay discounting and are partially associated with disruption of the frontal circuits, anorexia nervosa is associated with excessive control over food intake, decreased delay discounting, and exaggerated activity in dorsal cognitive circuits.

Study limitations included a relatively small number of studies for some disorders and the use of different criteria and scales to establish clinical diagnoses in studies, which may exaggerate heterogeneity between studies.

“Results of this study appear to provide empirical support for delay discounting as a transdiagnostic process across most of the psychiatric disorders examined,” researchers wrote, adding, “[The] literature search also revealed limited studies in some disorders, notably posttraumatic stress disorder, which is a priority area for research.”

Reference

Amlung M, Marsden E, Holshausen K, et al. Delay discounting as a transdiagnostic process in psychiatric disorders: a meta-analysis [published online August 28, 2019]. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2019.2102