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Bidirectional Relationship Between Methamphetamine Use and Positive Psychotic Symptoms in Regular Methamphetamine Users: Evidence From a Prospective Cohort Study
27 Pages Posted: 10 Oct 2018
More...Abstract
Background: Methamphetamine (MA) use is a major public health concern worldwide. MA has been causally associated with positive psychotic symptoms, but research is yet to determine if the reverse also occurs. This study prospectively determined whether the relationship between MA use and positive psychotic symptoms is bidirectional. The impact of lifetime psychotic disorders and MA dependence on these relationships was also examined.
Methods: This 12-month prospective study recruited a cohort of 201 regular (at least monthly use) primary MA users from free needle syringe programs in three Australian cities. Data on the frequency of MA use (Timeline Followback) and the severity of positive psychotic symptoms (Brief Psychiatric Rating Scale subscale) in the past 2 weeks were collected in 12 contiguous monthly face-to-face interviews. Diagnoses were derived using the Psychiatric Research Interview for DSM-IV Substance and Mental Disorders.
Outcomes: Participants had a mean age of 31.71 years (SD=8.10) and 38% (n=77) were female. At baseline 55% (n=110) were dependent on MA and 51% (n=101) had a lifetime psychotic disorder, comprised of 23% (n=23) primary and 77% (n=79) substance-induced psychotic disorders. Participants completed a mean of 9.14 (SD=3.16) out of the 11 follow up interviews were completed, 52% (n=104) completed all 11 interviews. Cross-lagged dynamic panel models were used to simultaneously test whether psychotic symptoms predicted higher levels of MA use in the next wave; and higher MA use predicted psychotic symptoms in the same next wave. This indicated there was a significant bidirectional relationship between psychotic symptoms and MA use (CFI = 0.94, RMSEA = 0.05 (95% CI = 0.04, 0.06). The magnitude of the relationship in each direction was similar, indicating neither direction predominated. This bidirectional relationship was found, regardless of whether participants had MA dependence or a lifetime psychotic disorder.
Interpretation: A bidirectional relationship between MA use and psychotic symptoms, of similar magnitude in each direction was found over one year. This highlights the dynamic and reciprocal nature of the relationship between MA and psychotic symptoms among MA users, and suggests integrated treatments that simultaneously target both of these variables may be of most benefit.
Funding Statement: This project was funded by an Australian National Health and Medical Research Council (NHMRC) Project Grant (APP326220). Leanne Hides and Maree Teesson are supported by NHMRC Senior Research and Principal Research Fellowships. Gary Chan and Rebecca McKetin are supported by University of Queensland and Curtin University Research Fellowships.
Declaration of Interests: The authors state: "The authors have no conflicts of interest."
Ethics Approval Statement: This project was approved by the relevant ethics review board and all participant provided written informed consent after receiving a description of the study.
Keywords: methamphetamine, psychotic symptoms, psychotic disorder, bidirectional, prospective
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