Dataset Information

Poor medication adherence and risk of relapse associated with continued cannabis use in patients with first-episode psychosis: a prospective analysis.

ABSTRACT:

Background

Cannabis use following the onset of first-episode psychosis has been linked to both increased risk of relapse and non-adherence with antipsychotic medication. Whether poor outcome associated with cannabis use is mediated through an adverse effect of cannabis on medication adherence is unclear.

Methods

In a prospective analysis of data acquired from four different adult inpatient and outpatient units of the South London and Maudsley Mental Health National Health Service Foundation Trust in London, UK, 245 patients were followed up for 2 years from the onset of first-episode psychosis. Cannabis use after onset of psychosis was assessed by self-reports in face-to-face follow-up interviews. Relapse data were collected from clinical notes using the WHO Life Chart Schedule. This measure was also used to assess medication adherence on the basis of both face-to-face interviews and clinical notes. Patients were included if they had a diagnosis of first-episode non-organic or affective psychosis according to ICD-10 criteria, and were aged between 18 and 65 years when referred to local psychiatric services. We used structural equation modelling analysis to estimate whether medication adherence partly mediated the effects of continued cannabis use on risk of relapse. The primary outcome variable was relapse, defined as admission to a psychiatric inpatient unit after exacerbation of symptoms within 2 years of first presentation to psychiatric services. Information on cannabis use over the first 2 years after onset of psychosis was investigated as a predictor variable for relapse. Medication adherence was assessed as a mediator variable on the basis of clinical records and self-report data. Study researchers (TS, NP, EK, and EF) rated the adherence.

Findings

397 patients who presented with their first episode of psychosis between April 12, 2002, and July 26, 2013 had a follow-up assessment until September, 2015. Of the 397 patients approached for followed up, 133 refused to take part in this study and 19 could not be included because of missing data. 91 (37%) of 245 patients with first-episode psychosis had a relapse over the 2 years of follow-up. Continued cannabis use predicted poor outcome, including risk of relapse, number of relapses, length of relapse, and care intensity at follow-up. In controlled structural equation modelling analyses, medication adherence partly mediated the effect of continued cannabis use on outcome, including risk of relapse (proportion mediated=26%, β_{indirect effects}=0·08, 95% CI 0·004 to 0·16), number of relapses (36%, β_{indirect effects}=0·07, 0·003 to 0·14), time until relapse (28%, β_{indirect effects}=-0·26, -0·53 to 0·001) and care intensity (20%, β_{indirect effects}=0·06, 0·004 to 0·11) but not length of relapse (6%, β_{indirect effects}=0·03, -0·03 to 0·09). The adjusted models explained moderate amounts of variance for outcomes defined as risk of relapse (R²=0·25), number of relapses (R²=0·21), length of relapse (R²=0·07), time until relapse (R²=0·08), and care intensity index (R²=0·15).

Interpretation

Between 20% and 36% of the adverse effects of continued cannabis use on outcome in psychosis might be mediated through the effects of cannabis use on medication adherence. Interventions directed at medication adherence could partly help mitigate the harm from cannabis use in psychosis.

Funding

This study is funded by the National Institute of Health Research (NIHR) Clinician Scientist award.

SUBMITTER: Schoeler T

PROVIDER: S-EPMC5522816 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:ObjectiveGuidelines for antipsychotic use in first-episode psychosis (FEP) recommend that medication be chosen initially on the basis of side effect profile with doses at the lower end of the range. Our objective was to describe the pattern of antipsychotic use in FEP over a period of 21 years in the context of changing clinical guidelines and the development of specialist early intervention in psychosis (EIP) services.SettingA community-based mental health service in South County Dublin (population 187 000) and a large private hospital.ParticipantsParticipants included 465 patients with FEP (146 from an epidemiological study (1995-1999) and 319 from a specialist EIP service (2005-2016)). Treatment with antipsychotic medication did not exceed 30 days at study entry.Outcome measuresThis is a descriptive study of prescribing practices in the context of service development and changing guidelines.ResultsFirst-generation antipsychotics were prescribed for 65% of the early cohort compared with 4.3% of the EIP cohort. Olanzapine was initially prescribed for 79.7% of EIP patients. Initial doses of medication were frequently low (≤50% British National Formulary (BNF) maximum) in both cohorts (71% and 78.6%). The demographic and clinical factors investigated did not influence the initial choice of antipsychotic medication significantly. Univariate logistic regression analysis suggested inpatient treatment setting was associated with a higher initial dose (>50% BNF maximum) of antipsychotic medication. Increasing dose requirements over the first month of engagement with an EIP service was associated with poorer global functioning at baseline, greater positive symptoms at baseline and the inpatient treatment setting. However, these associations were not seen in the multivariable model.ConclusionsSecond-generation antipsychotic prescribing predominates, but guidelines are often overlooked when choosing olanzapine notwithstanding lower initial dosages. EIP services should include proactive support for optimising medicines in line with evidence-based guidelines.