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Title: Continued cannabis use and risk of relapse in patients with a first episode psychosis
Author: Schoeler, Tabea
ISNI:       0000 0004 6347 6874
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2017
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Although cannabis use following a first episode of psychosis (FEP) has been linked to poor outcome such as relapse, current understanding is limited regarding the nature of this association. To shed light on the nature of this relationship, this thesis employed multiple methodological approaches: First, I pooled together data from previous studies in order to estimate the cross-sectional effects of continued and discontinued cannabis use following the onset of psychosis and risk of relapse, using a meta-analytic design (Paper 1). Second, I prospectively collected follow up data from a cohort of patients presenting with a first episode psychosis to psychiatric services in south London. Paper 2 examined the magnitude of effect of continued cannabis use on risk of relapse and related outcomes by grouping patients into classes of different patterns of cannabis use following onset of psychosis. In Paper 3, longitudinal modelling was employed to further examine whether the link between continued cannabis use and risk of relapse persists when non-causal explanations for the association are taken into account (reverse causation, premorbid genetic confounding). My findings indicate that that former regular users who stopped using cannabis after the onset had the most favourable illness course with regard to relapse. The most unfavourable course was present in those who continued to use high-potency cannabis in a high frequency manner. The results also suggest that this association reflects a dose-dependent association that is unlikely to be a result of reverse causation (e.g. selfmedication) or genetic and environmental (e.g. other illicit drug use, medication nonadherence) confounding. These findings point to reductions in cannabis use as a crucial interventional target to reduce risk of relapse in patients with a first episode psychosis.
Supervisor: Bhattacharyya, Sagnik ; Murray, Robin MacGregor Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available