Date Published: October 05, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Murat Yücel, Erin Oldenhof, Serge H. Ahmed, David Belin, Joel Billieux, Henrietta Bowden‐Jones, Adrian Carter, Samuel R. Chamberlain, Luke Clark, Jason Connor, Mark Daglish, Geert Dom, Pinhas Dannon, Theodora Duka, Maria Jose Fernandez‐Serrano, Matt Field, Ingmar Franken, Rita Z. Goldstein, Raul Gonzalez, Anna E. Goudriaan, Jon E. Grant, Matthew J. Gullo, Robert Hester, David C. Hodgins, Bernard Le Foll, Rico S. C. Lee, Anne Lingford‐Hughes, Valentina Lorenzetti, Scott J. Moeller, Marcus R. Munafò, Brian Odlaug, Marc N. Potenza, Rebecca Segrave, Zsuzsika Sjoerds, Nadia Solowij, Wim van den Brink, Ruth J. van Holst, Valerie Voon, Reinout Wiers, Leonardo F. Fontenelle, Antonio Verdejo‐Garcia.
The US National Institutes of Mental Health Research Domain Criteria (RDoC) seek to stimulate research into biologically validated neuropsychological dimensions across mental illness symptoms and diagnoses. The RDoC framework comprises 39 functional constructs designed to be revised and refined, with the overall goal of improving diagnostic validity and treatments. This study aimed to reach a consensus among experts in the addiction field on the ‘primary’ RDoC constructs most relevant to substance and behavioural addictions.
Forty‐four addiction experts were recruited from Australia, Asia, Europe and the Americas. The Delphi technique was used to determine a consensus as to the degree of importance of each construct in understanding the essential dimensions underpinning addictive behaviours. Expert opinions were canvassed online over three rounds (97% completion rate), with each consecutive round offering feedback for experts to review their opinions.
Seven constructs were endorsed by ≥ 80% of experts as ‘primary’ to the understanding of addictive behaviour: five from the Positive Valence System (reward valuation, expectancy, action selection, reward learning, habit); one from the Cognitive Control System (response selection/inhibition); and one expert‐initiated construct (compulsivity). These constructs were rated to be related differentially to stages of the addiction cycle, with some linked more closely to addiction onset and others more to chronicity. Experts agreed that these neuropsychological dimensions apply across a range of addictions.
The study offers a novel and neuropsychologically informed theoretical framework, as well as a cogent step forward to test transdiagnostic concepts in addiction research, with direct implications for assessment, diagnosis, staging of disorder, and treatment.
The aetiopathogeny of addiction remains poorly understood, as we lack assessment models to identify vulnerability to addiction. Only 10–20% of patients with substance and behavioural addictions receive treatment 1, 2, 3, which tend to have modest outcomes, reflected in low compliance and high relapse rates 4. Thus, there is an urgent need for alternative assessment and intervention strategies to prevent or reduce the personal, social and economic burden associated with addictions.
Utilizing Delphi methodology, experts identified a circumscribed set of RDoC constructs, as well as other novel dimensions central to understanding substance and behavioural addictions. In total, seven constructs reached consensus as being primary constructs in understanding addiction, including RDoC reward valuation, expectancy/reward prediction error, action selection/preference‐based decision‐making, reward learning, habit and response selection/inhibition. Compulsivity is not described in the RDoC (at least as a monodimensional construct) but was introduced by experts. Considerable evidence exists supporting compulsivity as a core feature of addiction (although see 68), representing an ongoing and repeated difficulty in refraining from drug‐seeking or ‐taking despite negative consequences. It is worth noting that the Positive Valence domain of the RDoC matrix recently underwent a reorganization (published online 28 June 2018), where both habit and aspects of compulsivity (‘reward valuation’) have been expanded upon, which should help in their incorporation when studying addictions.
The theoretical framework established in the current study provides a platform to test predictions that: (1) the majority of individuals with substance and behavioural addictions have specific dysfunctions in the primary constructs identified by our International Expert Consortium; (2) these dysfunctions cut across diagnostic boundaries (i.e. individuals from different addictions will cluster into the same neuropsychological phenotypes); and (3) these indices can be linked differentially to vulnerability and chronicity (i.e. stage of disorder). This framework may enable grouping of more homogeneous disorder subtypes, better linking of behavioural questionnaire phenotypes to neural, cellular and genetic dimensions, guiding clinical decisions to the core issues that drive addictions and measuring the success and failure of treatment (i.e. providing a clinical end‐point). It is envisioned that the findings will guide and fast‐track the development of a new generation of neuropsychological assessment tools, and improve the monitoring and effectiveness of both established and future novel interventions.