Impacts of recreational cannabis legalization on cannabis use: a longitudinal discordant twin study

Stephanie M Zellers; J. Megan Ross; Gretchen R Saunders; Jarrod M. Ellingson; Jacob E. Anderson; Robin P. Corley; William Iacono; John K. Hewitt; Christian J. Hopfer; Matt K. McGue; Scott Vrieze

doi:10.1111/add.16016

Impacts of recreational cannabis legalization on cannabis use: a longitudinal discordant twin study

Stephanie M Zellers, J. Megan Ross, Gretchen R Saunders, Jarrod M. Ellingson, Jacob E. Anderson, Robin P. Corley, William Iacono, John K. Hewitt, Christian J. Hopfer, Matt K. McGue, Scott Vrieze

Psychology (Twin Cities)

Research output: Contribution to journal › Article › peer-review

20 Scopus citations

Abstract

Aims: To estimate the effect of recreational legalization on cannabis use frequency and sources of variance across legal environments. Design: Longitudinal discordant twin and gene–environment interaction models in twins recruited from birth records and assessed prospectively. Setting: The United States, including states with different recreational cannabis policies before and after 2014, when recreational cannabis was first legalized. Participants: Two longitudinal, prospectively assessed samples of American twins aged 24–47 (n = 1425 in legal states, n = 1996 in illegal states), including 111 monozygotic pairs discordant for residence. Measurements: Current cannabis use frequency (measured continuously and ordinally) was the primary outcome, and the predictor was recreational status of cannabis (legal/illegal) in the participant’s state of residence at the time of assessment. Covariates include age, sex and cannabis use frequency prior to 2014. Findings: Accounting for pre-2014 use, residents of legal states used cannabis more frequently than residents of illegal states (b = 0.21, P = 8.08 × 10⁻⁵). Comparing 111 pairs of monozygotic twins discordant for residence confirmed the effect (b = 0.18, P = 0.014). There was inconclusive evidence for genetic influences on cannabis use frequency that were specific to the legal environment [χ² = 2.9 × 10⁻⁹, degrees of freedom (d.f.) = 1, P > 0.999]. Existing genetic influences were moderated by the legal environment, as the genetic correlation between marijuana use before and after legalization was lower in states that legalized (r_genetic = 0.24) compared with states that did not (r_genetic = 0.78, P_difference = 0.016). Conclusions: In the United States, there appears to be a ~ 20% average increase in cannabis use frequency attributable to recreational legalization, consistent across increasingly rigorous designs. In addition, the heritability of cannabis use frequency appears to be moderated by legalization.

Original language	English (US)
Pages (from-to)	110-118
Number of pages	9
Journal	Addiction
Volume	118
Issue number	1
DOIs	https://doi.org/10.1111/add.16016
State	Published - Jan 2023

Bibliographical note

Funding Information:
This work was supported by National Institutes of Health Grants (DA042755, DA046413, AA009367, MH066140, DA005147, DA013240, DA036216, AA023974, DA037904, DA032555, DA035804, DA011015, DA012845 and DA038065); the National Institute on Alcohol Abuse and Alcoholism at the National Institutes of Health (AA009367, AA023974); and the National Institute of Mental Health at the National Institutes of Health (MH066140).

Publisher Copyright:
© 2022 The Authors. Addiction published by John Wiley & Sons Ltd on behalf of Society for the Study of Addiction.

Keywords

Behavior genetics
causal inference
co-twin control
gene–environment interaction
natural experiment
substance use

PubMed: MeSH publication types

Twin Study
Journal Article
Research Support, N.I.H., Extramural

Publisher link

10.1111/add.16016License: CC BY-NC

Find It

Find It at U of M Libraries

Cite this

@article{36df3cdf5ae04767aa1f5b21c3b9a2e8,

title = "Impacts of recreational cannabis legalization on cannabis use: a longitudinal discordant twin study",

abstract = "Aims: To estimate the effect of recreational legalization on cannabis use frequency and sources of variance across legal environments. Design: Longitudinal discordant twin and gene–environment interaction models in twins recruited from birth records and assessed prospectively. Setting: The United States, including states with different recreational cannabis policies before and after 2014, when recreational cannabis was first legalized. Participants: Two longitudinal, prospectively assessed samples of American twins aged 24–47 (n = 1425 in legal states, n = 1996 in illegal states), including 111 monozygotic pairs discordant for residence. Measurements: Current cannabis use frequency (measured continuously and ordinally) was the primary outcome, and the predictor was recreational status of cannabis (legal/illegal) in the participant{\textquoteright}s state of residence at the time of assessment. Covariates include age, sex and cannabis use frequency prior to 2014. Findings: Accounting for pre-2014 use, residents of legal states used cannabis more frequently than residents of illegal states (b = 0.21, P = 8.08 × 10−5). Comparing 111 pairs of monozygotic twins discordant for residence confirmed the effect (b = 0.18, P = 0.014). There was inconclusive evidence for genetic influences on cannabis use frequency that were specific to the legal environment [χ2 = 2.9 × 10−9, degrees of freedom (d.f.) = 1, P > 0.999]. Existing genetic influences were moderated by the legal environment, as the genetic correlation between marijuana use before and after legalization was lower in states that legalized (rgenetic = 0.24) compared with states that did not (rgenetic = 0.78, Pdifference = 0.016). Conclusions: In the United States, there appears to be a ~ 20% average increase in cannabis use frequency attributable to recreational legalization, consistent across increasingly rigorous designs. In addition, the heritability of cannabis use frequency appears to be moderated by legalization.",

keywords = "Behavior genetics, causal inference, co-twin control, gene–environment interaction, natural experiment, substance use",

author = "Zellers, {Stephanie M} and Ross, {J. Megan} and Saunders, {Gretchen R} and Ellingson, {Jarrod M.} and Anderson, {Jacob E.} and Corley, {Robin P.} and William Iacono and Hewitt, {John K.} and Hopfer, {Christian J.} and McGue, {Matt K.} and Scott Vrieze",

note = "Funding Information: This work was supported by National Institutes of Health Grants (DA042755, DA046413, AA009367, MH066140, DA005147, DA013240, DA036216, AA023974, DA037904, DA032555, DA035804, DA011015, DA012845 and DA038065); the National Institute on Alcohol Abuse and Alcoholism at the National Institutes of Health (AA009367, AA023974); and the National Institute of Mental Health at the National Institutes of Health (MH066140). Publisher Copyright: {\textcopyright} 2022 The Authors. Addiction published by John Wiley & Sons Ltd on behalf of Society for the Study of Addiction.",

year = "2023",

month = jan,

doi = "10.1111/add.16016",

language = "English (US)",

volume = "118",

pages = "110--118",

journal = "Addiction",

issn = "0965-2140",

publisher = "Blackwell Publishing Ltd",

number = "1",

}

TY - JOUR

T1 - Impacts of recreational cannabis legalization on cannabis use

T2 - a longitudinal discordant twin study

AU - Zellers, Stephanie M

AU - Ross, J. Megan

AU - Saunders, Gretchen R

AU - Ellingson, Jarrod M.

AU - Anderson, Jacob E.

AU - Corley, Robin P.

AU - Iacono, William

AU - Hewitt, John K.

AU - Hopfer, Christian J.

AU - McGue, Matt K.

AU - Vrieze, Scott

N1 - Funding Information: This work was supported by National Institutes of Health Grants (DA042755, DA046413, AA009367, MH066140, DA005147, DA013240, DA036216, AA023974, DA037904, DA032555, DA035804, DA011015, DA012845 and DA038065); the National Institute on Alcohol Abuse and Alcoholism at the National Institutes of Health (AA009367, AA023974); and the National Institute of Mental Health at the National Institutes of Health (MH066140). Publisher Copyright: © 2022 The Authors. Addiction published by John Wiley & Sons Ltd on behalf of Society for the Study of Addiction.

PY - 2023/1

Y1 - 2023/1

N2 - Aims: To estimate the effect of recreational legalization on cannabis use frequency and sources of variance across legal environments. Design: Longitudinal discordant twin and gene–environment interaction models in twins recruited from birth records and assessed prospectively. Setting: The United States, including states with different recreational cannabis policies before and after 2014, when recreational cannabis was first legalized. Participants: Two longitudinal, prospectively assessed samples of American twins aged 24–47 (n = 1425 in legal states, n = 1996 in illegal states), including 111 monozygotic pairs discordant for residence. Measurements: Current cannabis use frequency (measured continuously and ordinally) was the primary outcome, and the predictor was recreational status of cannabis (legal/illegal) in the participant’s state of residence at the time of assessment. Covariates include age, sex and cannabis use frequency prior to 2014. Findings: Accounting for pre-2014 use, residents of legal states used cannabis more frequently than residents of illegal states (b = 0.21, P = 8.08 × 10−5). Comparing 111 pairs of monozygotic twins discordant for residence confirmed the effect (b = 0.18, P = 0.014). There was inconclusive evidence for genetic influences on cannabis use frequency that were specific to the legal environment [χ2 = 2.9 × 10−9, degrees of freedom (d.f.) = 1, P > 0.999]. Existing genetic influences were moderated by the legal environment, as the genetic correlation between marijuana use before and after legalization was lower in states that legalized (rgenetic = 0.24) compared with states that did not (rgenetic = 0.78, Pdifference = 0.016). Conclusions: In the United States, there appears to be a ~ 20% average increase in cannabis use frequency attributable to recreational legalization, consistent across increasingly rigorous designs. In addition, the heritability of cannabis use frequency appears to be moderated by legalization.

AB - Aims: To estimate the effect of recreational legalization on cannabis use frequency and sources of variance across legal environments. Design: Longitudinal discordant twin and gene–environment interaction models in twins recruited from birth records and assessed prospectively. Setting: The United States, including states with different recreational cannabis policies before and after 2014, when recreational cannabis was first legalized. Participants: Two longitudinal, prospectively assessed samples of American twins aged 24–47 (n = 1425 in legal states, n = 1996 in illegal states), including 111 monozygotic pairs discordant for residence. Measurements: Current cannabis use frequency (measured continuously and ordinally) was the primary outcome, and the predictor was recreational status of cannabis (legal/illegal) in the participant’s state of residence at the time of assessment. Covariates include age, sex and cannabis use frequency prior to 2014. Findings: Accounting for pre-2014 use, residents of legal states used cannabis more frequently than residents of illegal states (b = 0.21, P = 8.08 × 10−5). Comparing 111 pairs of monozygotic twins discordant for residence confirmed the effect (b = 0.18, P = 0.014). There was inconclusive evidence for genetic influences on cannabis use frequency that were specific to the legal environment [χ2 = 2.9 × 10−9, degrees of freedom (d.f.) = 1, P > 0.999]. Existing genetic influences were moderated by the legal environment, as the genetic correlation between marijuana use before and after legalization was lower in states that legalized (rgenetic = 0.24) compared with states that did not (rgenetic = 0.78, Pdifference = 0.016). Conclusions: In the United States, there appears to be a ~ 20% average increase in cannabis use frequency attributable to recreational legalization, consistent across increasingly rigorous designs. In addition, the heritability of cannabis use frequency appears to be moderated by legalization.

KW - Behavior genetics

KW - causal inference

KW - co-twin control

KW - gene–environment interaction

KW - natural experiment

KW - substance use

UR - http://www.scopus.com/inward/record.url?scp=85136796148&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85136796148&partnerID=8YFLogxK

U2 - 10.1111/add.16016

DO - 10.1111/add.16016

M3 - Article

C2 - 36002928

AN - SCOPUS:85136796148

SN - 0965-2140

VL - 118

SP - 110

EP - 118

JO - Addiction

JF - Addiction

IS - 1

ER -

Impacts of recreational cannabis legalization on cannabis use: a longitudinal discordant twin study

Abstract

Bibliographical note

Keywords

PubMed: MeSH publication types

Publisher link

Find It

Other files and links

Fingerprint

Cite this