A transdiagnostic dimensional approach towards a neuropsychological assessment for addiction: an international Delphi consensus study

Abstract

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Keywords: Addiction; RDoC; assessment; cognition; compulsions; decision-making; habit; reward; transdiagnostic.

Figure 1

Overview of the Research Domain Criteria (RDoC) schema highlighting the five major domains, comprising 23 main constructs (bold text), wherein seven of these main constructs are further broken down into 23 subconstructs (italicized text), leading to a total of 39 primary and subconstructs. Note that in June 2018 (after the immediate completion of this paper), the Positive Valence domain of the RDoC matrix underwent a reorganization. The original constructs used in this study are mostly retained, but have been reorganized somewhat differently (see https://www.nimh.nih.gov/about/advisory‐boards‐and‐groups/namhc/reports/rdoc‐changes‐to‐the‐matrix‐cmat‐workgroup‐update‐proposed‐positive‐valence‐domain‐revisions.shtml)

Figure 2

A flow‐chart of the constructs over each round highlighting items that were endorsed by ≥ 80% of experts as being clearly relevant (i.e. primary constructs; included items listed on the left together with percentage of experts endorsing the item), not relevant to addiction (excluded), created (i.e. new constructs, indicated by the asterisk), or re‐rated over the three survey rounds. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 3

An overview of the consensus level and range for all 39 Research Domain Criteria (RDoC) (sub)constructs and seven additional constructs suggested by the experts for inclusion. All constructs were investigated over three rounds (only the first two rounds are shown, as the seven essential domains were derived in these rounds—all items in round three were excluded; percentages calculated relative to the total number reported). Note that expert‐suggested constructs were included in round 2 (bottom seven items in the list of constructs); the red highlight indicates the constructs that were selected as ‘Primary’ across the two rounds. V.Important = very important; M.Important = moderately important; S.Important = somewhat important; I = initial; S = sustained; V = visual; A = auditory; O/S = olfactory/somatosensory; D = declarative; R = reception; P = production; Expectancy = expectancy/reward prediction error; Action Selection = action selection/preference‐based decision‐making; Response Selection = response selection/inhibition

Figure 4

Experts’ endorsements for stages of disorder for primary constructs

Figure 5

Expert‐endorsed primary constructs as a function of the major Research Domain Criteria (RDoC) domains (green = positive valence system; red = negative valance system; blue = cognitive system) and the constructs within these domains that are most relevant to the process of addiction (i.e. as a function of the relative size/width of the circles). Also illustrated are the relative influences of the seven primary constructs on the vulnerability to or the chronicity of addiction