- Title
- Cigarette smoking and psychosis: an examination of motivations and cognitive factors
- Creator
- Clark, Vanessa
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2015
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Tobacco smoking is one of the leading modifiable risk factors for chronic disease including cardiovascular disease, cancers and lung related diseases. Despite the declining smoking rates among the general population, smoking rates among those with psychosis have remained stable and high. Individuals with psychosis have very high rates of cigarette smoking and nicotine dependence. They have longer demonstrated smoking histories compared to those without a psychotic disorder and tend to smoke stronger cigarettes, more frequently. The elevated smoking amongst this population in combination with a reduced quit rate places this clinical population at a higher risk of cardiovascular related diseases and as a result, a significantly reduced life expectancy. Cigarette smoking also increases the metabolism of some antipsychotic medications, requiring smokers with schizophrenia to take larger doses to achieve the same therapeutic levels compared to those who do not smoke. This leads to an increase in the number and severity of medication side effects, as well as reducing the therapeutic benefits of these medications. The factors that may affect smoking in psychosis are complex and speculative, and the high rates of smoking are still a pertinent issue. Two major theories that attempt to explain the high rates of smoking amongst those with psychosis are the self-medication hypothesis and the addiction vulnerability hypothesis. The self-medication hypothesis refers to the theory that people with psychosis smoke cigarettes to correct an underlying deficit in their neuropathology and to treat the symptoms of their illness. The addiction vulnerability hypothesis argues that abnormalities in the brain reward pathways may make people with psychosis more vulnerable to smoking, but does not specify whether smoking provides any therapeutic benefits for those with psychosis. The aim of this thesis is to understand the motivations that may encourage smoking initiation and maintenance among those with psychosis. There will be a focus on the self-medication hypothesis and the addiction vulnerability hypothesis, with reference to subjective reasons for cigarette smoking, as well as potential cognitive motivators. A multifaceted approach was employed to address these questions in various samples with established and early psychosis, examining (1) self-reported reasons for smoking and how these influence smoking cessation; (2) the influence of smoking on clinical and cognitive outcomes in young people at ultra-high risk of psychosis or early psychosis; and (3) the influence of smoking on a well-characterised cognitive deficit in people with schizophrenia, visual spatial working memory (VSWM). The findings of this thesis illustrate that there is a clear association between smoking and psychosis. Subjective data were supportive of the self-medication hypothesis, in that participants with psychosis who endorsed more reasons for smoking associated with activation and stimulation motives showed reduced quit rates compared to those who endorsed fewer of these reasons. The activation and stimulation reasons were also correlated with illness measures, indicating that when a person is more unwell, they endorse this set of reasons for smoking at greater levels, which has a flow on effect of a lower rate of smoking cessation success. The results of this thesis clearly demonstrate that above treatment related and demographic influences (intensity of smoking cessation intervention, psychosis diagnosis and number of cigarettes smoked per day and age), self-reported reasons for smoking are a predictor of short-term abstinence and are related to clinical symptoms. In addition, this thesis found evidence for the addiction vulnerability hypothesis demonstrating that cigarette smoking is related to transition to psychosis. The relationship may be mediated through a relationship between early psychosis and cognitive deficits, which are common in early psychosis. Although, there was no evidence of a benefit of cigarette smoking for young people with psychosis or at risk for psychosis on the cognitive domains of attention, verbal memory, visual memory, working memory or reasoning and problem solving. Given the interaction that smoking appears to have with cognition in regards to transition to psychosis, it is plausible that the effect that cigarette smoking has on transition is being mediated through nicotine’s effect on cognition. This suggests that smoking may not be a marker of transition per se, but a side effect of deficits in cognition. The effect of smoking status on transition to psychosis occurred independently of baseline comorbid substance use, including cannabis. Those who had early psychosis were also more likely to be current smokers compared to those at ultra-high risk of psychosis or those with other mental health problems (such as anxiety or depression). There was no strong evidence for the self-medication hypothesis for smoking in schizophrenia for the cognitive domain of VSWM from the experimental paradigm, and limited support from the systematic review. Differences in study design (between subjects versus within subjects) appear to explain some of the differences in findings of the systematic review. The within subjects designs (abstinent versus ad libitum smoking design), appeared to be the most sensitive method of exposing the effects of nicotine in VSWM. However, when this design was employed in the experimental component of this thesis, improvements on tasks of VSWM once smoking was reinstated were not observed. Whilst this thesis suggests that there is a link between smoking and psychosis, this should not serve as a justification for smoking to remain untreated in this group. To the contrary the results of this thesis should be used to inform future smoking cessation interventions and target future research to examine this issue from a different perspective. For example, tailoring smoking cessation interventions to those with a psychotic disorder, including addressing self-reported reasons for smoking in the early stages of smoking cessation interventions and using these reasons to address any relevant barriers to quitting. In addition, smoking cessation interventions should target those at risk of psychosis or in the early stages of a psychotic illness. To date there are no studies published in this area. More research should also be directed at the addiction vulnerability hypothesis, as well as the self-medication hypothesis. It is important to understand the complexities of smoking and psychosis so that the morbidity and mortality that is currently associated with those with psychosis from preventable diseases might be able to reduce, and increases to quality of life gained.
- Subject
- smoking; psychosis; cognition
- Identifier
- http://hdl.handle.net/1959.13/1296527
- Identifier
- uon:19276
- Rights
- Copyright 2015 Vanessa Clark
- Language
- eng
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