National Amphetamine-Type Stimulant Strategy Background Paper: Monograph Series No. 69
3.3 Dependence and adverse outcomes
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3.3 Dependence and adverse outcomes
ATS users can become dependent and ATS dependence is associated with a range of physical and mental health problems. According to the Diagnostic and Statistical Manual of Mental Disorders (DSM; American Psychiatric Association, 2000), dependence is characterised by experience of at least three of the following symptoms:
- tolerance, which is defined as either a need to use larger amounts of the substance to achieve desired effect, or decreased effect with continued use of the same amount;
- withdrawal;
- increased dosage and duration of the substance use;
- unsuccessful attempts to cut down or control substance use;
- increased time spent to obtain the substance, use the drug or come down from the drug;
- giving up social, occupational and recreational activities because of substance use; and
- continued substance use despite awareness of its negative consequences (e.g., physical or psychological problems).
It has been estimated that the number of regular methamphetamine users in Australia is 102,600 and of these, 72,700 have been estimated to be methamphetamine dependent (McKetin et al., 2005). It has been suggested that the newer crystalline form of methamphetamine may lead to greater dependence compared to other forms. This issue was recently investigated in a sample of 309 regular methamphetamine users in Sydney (McKetin, Kelly & McLaren, 2006). Using the Severity of Dependence Scale, this study found that participants who had used crystal methamphetamine in the past year were significantly more likely to be dependent on methamphetamine compared to those who had only taken other forms of methamphetamine during this time. Furthermore, methamphetamine dependence was found to be associated with injecting or smoking as methods of use, using more than weekly, and a history of use over 5 years. Even after adjusting for these patterns of use, crystal methamphetamine use remained significantly associated with methamphetamine dependence.
A study by Kalechstein and colleagues (2003) produced the first findings to demonstrate that methamphetamine dependence is associated with impairments across a range of neurocognitive domains. Methamphetamine dependent users abstinent for 5 to 14 days performed significantly worse than controls on neurocognitive measures sensitive to attention/ psychomotor speed, verbal learning and memory, and executive systems measures sensitive to fluency. These differences were not attributable to demographics, estimated premorbid IQ, and level of self-reported depression. Research investigating the methamphetamine market in Sydney found that dependence on methamphetamine was the key predictor of poor physical and mental health among users (McKetin, McLaren & Kelly, 2005).
Other recent research has added to the understanding of the relationship of meth/amphetamine dependence to adverse outcomes. For example, Dyer and Cruickshank (2005) explored the psychological profile among 218 admissions to an inpatient methamphetamine detoxification program. It was found that approximately 46% of methamphetamine-dependent inpatients had been previously diagnosed for a psychological health problem, with approximately 30% requiring admission to a psychiatric hospital. In a second study the Beck Depression Inventory II (BDI-II; Beck et al., 1996) was administered to 367 outpatients receiving treatment for methamphetamine or heroin dependence. The mean total BDI-II score was reported to be in the moderate range. It was found that methamphetamine-dependent patients’ total BDI-II score was similar to that of psychiatric outpatients with clinical depression, but significantly greater than psychiatric outpatients with anxiety disorders.
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Psychiatric problems appear to occur predominantly among dependent methamphetamine users, rather than among those who take the drug infrequently. To further illustrate this, a recent Australian conference was presented with research conducted with a large community sample of amphetamine users in Queensland (Conroy, 2006). It was noted that 42% of those who were amphetamine dependent, compared to 21% of non-dependent amphetamine users, had recently experienced moderate to severe mental health disability. Overall, dependent users had higher levels of depression and anxiety, more easily lost their temper and had poor relationships.
Based on their own research and a review of the literature, McKetin and Mattick (1997) concluded that:
- Dependence on amphetamine has been associated with poor psychological health, especially in younger individuals who frequently use large amounts of amphetamine…. Psychological problems reported by amphetamine users included feeling scattered, vague, distracted and problems with concentration that impeded work performance or study….The results of this study show that severely dependent amphetamine users suffer from poor memory and concentration, performing from half to one standard deviation worse on WMS-R indices than less dependent amphetamine users. This study also found preliminary evidence that a history of heavy amphetamine use, particularly injecting more than 3-4 days per week, was associated with impairment of visual memory tasks (pp.235, 240).
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