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Regression to the mean in substance use disorder treatment research
Author(s) -
Finney John W.
Publication year - 2008
Publication title -
addiction
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.424
H-Index - 193
eISSN - 1360-0443
pISSN - 0965-2140
DOI - 10.1111/j.1360-0443.2007.02032.x
Subject(s) - regression toward the mean , equating , treatment and control groups , vulnerability (computing) , psychology , population , regression , affect (linguistics) , matching (statistics) , treatment effect , medicine , clinical psychology , psychiatry , statistics , computer science , developmental psychology , psychotherapist , mathematics , computer security , environmental health , communication , pathology , rasch model , traditional medicine
Aims Regression to the mean (RTM) refers to the tendency for a group of cases that differ from the population mean to move (regress) towards the mean, on average, when re‐assessed, if scores at the two points are less than perfectly correlated. This paper considers factors that affect the magnitude of RTM and how RTM may impact findings from primary studies and reviews of substance use disorder (SUD) treatment. Design and methods The paper is guided largely by A Primer on Regression Artifacts by Campbell and Kenny. It reviews potential RTM effects in three areas of SUD treatment research. One is the extent to which within‐group improvement in comparative treatment trials, including ‘placebo effects’, is a function of RTM. The second is the vulnerability of treatment evaluations employing non‐equivalent control group designs to RTM and biased estimates of treatment effects when matching, or statistical equating is used to adjust for pre‐existing group differences. The final issue is the impact of RTM in syntheses of research findings on SUD treatments. In particular, the tendency for later studies of a particular intervention to have smaller treatment effect sizes relative to earlier studies is considered as an RTM phenomenon. Findings RTM is a pervasive, but often unrecognized phenomenon that can bias findings in SUD treatment studies and in systematic reviews of that research. Conclusion SUD treatment researchers should be aware of RTM, take any available steps to reduce it, and try to diagnose whether it is still affecting research findings.