Elsevier

Drug and Alcohol Dependence

Volume 187, 1 June 2018, Pages 363-369
Drug and Alcohol Dependence

Full length article
Relationship between the duration of methamphetamine use and psychotic symptoms: A two-year prospective cohort study

https://doi.org/10.1016/j.drugalcdep.2018.03.023Get rights and content

Highlights

  • Psychotic symptoms were more common during methamphetamine (MA) use.

  • A dose-response effect exists between MA use length and risk of psychotic symptoms.

  • The effect was observed among those without psychotic symptoms at baseline.

  • This study supports reduction of MA use to reduce psychotic symptoms.

Abstract

Background

Psychosis is a key harm associated with methamphetamine (MA) use. This study examined the relationship between the duration of MA use and risk of psychotic symptoms.

Methods

A cohort of 528 individuals with chronic MA use was followed for two years after leaving treatment center in Guangdong, China. Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale at baseline and four follow-up visits (6, 12, 18 and 24 months after baseline). MA use during the past six months was investigated at each assessment. Generalized Estimating Equations for longitudinal panel data were developed to examine the risk of MA-associated psychotic symptoms among individuals with different durations of MA use. 340 MA users who completed at least one follow-up were included in the analysis.

Results

During 6-month intervals, participants who reported MA use showed a two-fold increase in the risk of psychotic symptoms compared to those with no MA use (odds ratio [OR] = 2.15, 95% confidence interval [CI] = 1.33–3.49). A dose-response effect was found between the duration of MA use and the risk of psychotic symptoms (continued 12-month MA use vs. no use: OR = 2.84, 95% CI = 1.39–5.77; continued 18-month MA use vs. no use: OR = 9.93, 95% CI = 3.58–27.57). There was no assessment for 24-month intervals due to a small sample size of the continuous use group.

Conclusions

Longer periods of MA use predicted a higher risk of experiencing psychotic symptoms. Early prevention of MA use could help reduce the risk of psychosis in MA users.

Introduction

The increasing popularity of amphetamine-type stimulants (ATS), particularly methamphetamine (MA), has become a major concern for global health experts. The World Drug Report 2016 showed that 35.7 million individuals used ATS in 2014, making ATS the second most commonly consumed class of drugs after cannabinoids. Methamphetamine-induced seizures accounted for the largest share of global ATS-induced seizures (United Nations Office on Drugs and Crime, 2016). Methamphetamine continues to dominate the market for ATS, especially in East and Southeast Asia (United Nations Office on Drugs and Crime, 2016). China has experienced a recent surge in MA use, and ATS have become the leading drug of abuse in China (Sun et al., 2014). Among registered illicit drug users, the proportion of individuals who use synthetic drugs – mostly ATS and ketamine – exceeded the number of heroin users in 2015, and the figure totaled 60.5% in 2016 (Office of China National Narcotic Control Commission, 2017).

A major health consequence of MA use is its association with the experience of psychotic symptoms (Harro, 2015), such as persecutory delusions and auditory hallucinations (Fasihpour et al., 2013). Research has estimated that the prevalence of psychotic symptoms among MA users is between 13% and 24% (McKetin et al., 2006; Salo et al., 2011; Sulaiman et al., 2014). The presence of MA-related psychotic symptoms is more common in MA users who are dependent on MA than those who are not (McKetin et al., 2006). Individuals with MA-related psychosis present high rates of later developing schizophrenia (Niemi-Pynttari et al., 2013) and other poor outcomes, including other serious psychiatric disorders (Eslami-Shahrbabaki et al., 2015), high health service utilization (Glasner-Edwards et al., 2008), and a high risk of premature death and suicidal behaviors over long-term follow-up (Kittirattanapaiboon et al., 2010). Considering the numerous negative consequences of MA-related psychosis, it is necessary to examine the factors that affect the development of psychosis in those who use MA to prevent and reduce its incidence.

Previous studies identified several factors that are associated with the presence, severity, and/or persistence of MA-related psychosis, including the intensity of MA use (Ding et al., 2014; Lichlyter et al., 2011; McKetin et al., 2006), a history of psychotic disorder (McKetin et al., 2006), a family history of psychosis (Chen et al., 2005), a family history of other mental illness (Farnia et al., 2016), psychiatric comorbidity (e.g., depression, bipolar disorder, and antisocial personality disorder) (McKetin et al., 2016; Sulaiman et al., 2014), and childhood adverse events (Ding et al., 2014). Psychotic symptoms vary as a function of differences in the amount, form, frequency, and duration of MA use (Ding et al., 2014; Lappin et al., 2016; Salo et al., 2013; Sulaiman et al., 2014). A dose-dependent relationship was found between the frequency of MA use and the risk for psychotic symptoms over a four-week period in one small cohort study (McKetin et al., 2013). Retrospective data from cross-sectional studies indicate that subjects with more years of chronic MA use had a higher prevalence and greater severity of psychosis (Ding et al., 2014; Lichlyter et al., 2011). However, the dose response link between the duration of MA use and the risk of developing psychotic symptoms over time is unknown. A better understanding of the prospective link between the duration of MA use and psychotic symptoms in larger longitudinal studies is important to inform both the detection and early treatment of MA-related psychotic symptoms. Thus, the present study examined the prospective relationship between the duration of MA use and psychotic symptoms, based on a two-year follow-up of a cohort of adults with chronic MA use.

Section snippets

Participants and procedure

The present study was part of a prospective cohort study that collected data on the prevalence, incidence, and risk factors of human immunodeficiency virus (HIV) and hepatitis C virus (HCV) infection in a sample of individuals who had recently used synthetic drugs and who were about to leave treatment centers (Wang et al., 2017). A total of 528 individuals with chronic MA use were recruited at baseline from compulsory and voluntary drug detoxification and rehabilitation centers in Guangdong

Sample characteristics

During the two-year follow-up period, 167 (31.6%) MA users were lost to follow-up (e.g., not participating in any follow-up interview) due to loss of contact. Twenty-one (4.0%) MA users who did not provide data on MA use or psychotic symptoms at follow-up interviews were excluded. Thus, a total of 340 MA users who completed at least one follow-up assessment were included in our analysis.

Of the 340 MA users included in the analysis, 245 (72.1%) completed four follow-up measurements of MA use and

Discussion

The present two-year longitudinal study found that the risk of experiencing psychotic symptoms was twice as high during periods of MA use compared with no use. As the duration of MA exposure increased, the odds of experiencing psychotic symptoms also increased, such that continued MA use over 18 months increased the odds of psychotic symptoms ten-fold compared with no use over the same period. We found a clear dose-response effect of continued MA use on the risk of psychotic symptoms. This

Contributors

Ms. Ma and Bao had full access to all the data in the study and took responsibility for the integrity of the data and the accuracy of the data analyses. Concept and design: Ma, Wang, Li, Shi, Bao and Lu. Acquisition, analysis, or interpretation of data: Ma, Wang, Meng, Wu. Drafting of the manuscript: Ma. Critical revision of the manuscript for important intellectual content: Profs. Blow, Ilgen, Degenhardt, Lappin, Shi, Bao and Lu. Statistical analysis: Ma, Wang. Supervision: Profs. Bao and Lu.

Role of funding sources

This work was supported by the Thirteenth Five-Year Program of the Chinese Ministry of Science and Technology [no. <gn1 > 2016YFC0800907</gn1>] and the State Scholarship Fund of China [no. <gn2 > 201706015001</gn2>]. The funding organizations had no role in the study design, collection, analysis, or interpretation of the data, writing the manuscript, or the decision to submit the paper for publication.

Conflict of interest

None.

Acknowledgements

The authors wish to thank all the interviewers and participants for their cooperation

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