Factors associated with variability and stability of cannabis use in young adulthood
Introduction
In developed countries, cannabis use is generally concentrated among young adults (Australian Institute of Health and Welfare, 2011, European Monitoring Centre for Drugs and Drug Addiction, 2009, Substance Abuse and Mental Health Services Administration, 2010). Data from the United States showed that past month prevalence was highest (18%) among 18–25 year olds (SAMHSA, 2010). European prevalence estimates suggest the highest levels of past year cannabis use (16%, on average) were among individuals aged 15–24 years (European Monitoring Centre for Drugs and Drug Addiction, 2009). In Australia, one in five (21%) 20–29 year olds have used cannabis in the past year and 29% of these individuals used the drug at least weekly; past month prevalence was also highest (11%) among this age group (Australian Institute of Health and Welfare, 2011). Although many young adults typically ‘mature out’ of cannabis use (Kandel and Logan, 1984, von Sydow et al., 2001), a substantial minority of more entrenched users persist with use of the drug (Swift et al., 2008) and may experience a range of adverse consequences (Hall, 2001).
The literature on cannabis use is dominated by research that has focused on early-life and adolescent risk factors. Childhood factors such as parental substance use and childhood poverty and sexual abuse have been implicated in cannabis use (Melchior et al., 2011, Nelson et al., 2006). Adolescent smoking (Hayatbakhsh et al., 2009, Lewisohn et al., 1999) and alcohol consumption (Hayatbakhsh et al., 2009) have been associated with cannabis use and dependence in early young adulthood. Sparse research suggests the association may extend into adulthood (Aitken et al., 2000, DiNitto and Choi, 2011, Kandel, 1984). Heavy cannabis use has been associated with an increased risk of depression and anxiety in young adulthood (Arseneault et al., 2002, Cheung et al., 2010, Hayatbakhsh et al., 2007, Patton et al., 2002, van Laar et al., 2007). Personality factors related to sensation seeking (Crawford et al., 2003, Franken and Muris, 2006, Martins et al., 2008) and novelty seeking (Adams et al., 2003, Evren et al., 2007) have been commonly associated with substance use. Peer drug use (van den Bree and Pickworth, 2005, von Sydow et al., 2002) and negative peer interactions such as conflict and hostility within friendships have been associated with increased substance use (Branstetter et al., 2011). Protective factors identified include attachment to the family, low parental conflict and religious involvement (Loxley et al., 2004).
While research interest in young adults has grown, improved knowledge of the factors associated with cannabis use at this time is important for developing treatment strategies for this group. To date, however, few longitudinal studies have investigated factors in young adulthood which are associated with patterns of cannabis use after the peak period of experimentation. This is an important area of research as the period of risk for initiation is extending beyond adolescence (Degenhardt et al., 2008) and young adulthood is a period of relatively active cannabis use (Australian Institute of Health and Welfare, 2011, European Monitoring Centre for Drugs and Drug Addiction, 2009, Substance Abuse and Mental Health Services Administration, 2010). Moreover, prevention programmes are increasingly taking a developmental pathways approach (Toumbourou et al., 2007). This approach recognises that risk factors for cannabis use can emerge throughout the life-course and the opportunity to influence adverse developmental pathways can be extended beyond childhood and adolescence (Loxley et al., 2004, Lynch, 2000).
The aims of the study were to identify and compare the most important factors in young adulthood associated with: (1) initiating cannabis use, (2) reverting to cannabis use, and (3) remaining a cannabis user in young adulthood. Identifying young adults at increased risk of these patterns of cannabis use is fundamental to developing prevention and treatment strategies for this group. The longitudinal design enabled change in cannabis use in young adulthood to be predicted based on factors assessed approximately four years prior. To date, it is the first study of this kind in an Australian sample.
Section snippets
Sample
Data were analysed from two waves (wave one, mean age 23 years, range 20–26, SD 1.51; wave two, mean age 27 years, range 24–30, SD 1.50) of the 20+ year cohort from PATH (Rodgers et al., 2005). PATH is a community-based longitudinal survey of people randomly drawn from the electoral roll of the Australian Capital Territory and nearby Queanbeyan, New South Wales. The main questionnaire was self-complete with cognitive and physical tests administered by a trained interviewer. Of the 2404
Sample
Approximately half (48%) the sample was male (Table 1). The majority were Caucasian (93%) and had completed secondary school (92%). Physical (78%) and mental (74%) health were generally unimpaired. Forty-two percent of people were at-risk drinkers and 31% smoked tobacco.
Pattern of cannabis use
Eight patterns of cannabis use in young adulthood were identified (Table 2). Among cannabis non-users at age 23 years (n = 617), approximately one in five (19%) had initiated use of the drug by age 27 years (initiated use). Of
Discussion
This is the first study to investigate the factors associated with variability and stability of cannabis use in a large representative sample of young Australian adults followed prospectively. The findings contribute to knowledge of the natural history of cannabis use. Among this group, one in five used cannabis for the first time in young adulthood but use was generally short-term or infrequent. The resumption of use after an extended period of non-use (i.e., at least 12 months) was not
Role of funding source
This work was supported by a scholarship which was provided by Professor Richard Mattick (National Drug and Alcohol Research Centre; University of New South Wales). The National Drug and Alcohol Research Centre at the University of NSW is supported by funding from the Australian Government under the Substance Misuse Prevention and Service Improvements Grants Fund. Funding sources had no further role in: study design; the collection, analysis or interpretation of data; in the writing of the
Contributors
Authors Silins, Hutchinson, Swift, Slade and Toson made substantial contributions to conception, secondary analysis and interpretation of data. Author Rodgers made a substantial contribution to the acquisition of the data. Author Silins drafted, reviewed and revised all versions of the article. Author Toson reviewed early drafts. Authors Hutchinson, Swift, Slade and Rodgers revised the article critically for important intellectual content. All authors have approved the final version to be
Conflict of interest
No conflict declared.
Acknowledgments
The involvement of Trish Jacomb and the team at the Centre for Mental Health Research (Australian National University) is gratefully acknowledged. This work was supported by a scholarship which was provided by Professor Richard Mattick (National Drug and Alcohol Research Centre; University of New South Wales). The National Drug and Alcohol Research Centre at the University of NSW is supported by funding from the Australian Government under the Substance Misuse Prevention and Service
References (63)
- et al.
Relationships between personality and preferred substance and motivations for use among adolescent substance abusers
Am. J. Drug Alcohol Abuse
(2003) - et al.
A twin study of personality and illicit drug use and abuse/dependence
Twin Res.
(2004) - et al.
Are there genetic influences on addiction: evidence from family, adoption and twin studies
Addiction
(2008) - et al.
Correlates of later-onset cannabis use in the National Epidemiological Survey on Alcohol and Related Conditions (NESARC)
Drug Alcohol Depend.
(2009) - et al.
Marijuana use among adults: a longitudinal study of current and former users
J. Subst. Abuse
(2000) - et al.
Cannabis use in adolescence and risk for adult psychosis: longitudinal prospective study
Br. Med. J.
(2002) General Practice Activity in Australia 1998–99 to 2007–08: 10 Year Data Tables
(2008)2010 National Drug Strategy Household Survey Report. Drug Statistics Series Number 25
(2011)- et al.
The Decline of Substance Use in Young Adulthood: Changes in Social Activities, Roles, and Beliefs
(2002) - et al.
Family, religiosity, and the risk of adolescent drug use
J. Marriage Fam.
(1998)