Cannabis and mental health problems

Abstract

On a global scale, cannabis is the most commonly used illicit drug with around 5 000 000 people using on a daily basis. Although the Home Office has documented that cannabis use in the UK has declined in the last couple of years, the last decade has seen increasing popularity in the use of synthetic cannabinoids (known as ‘spice’). These are marketed online as innocuous herbal products. Several authors have provided evidence to suggest that cannabis use (including ‘spice’) is a cause of mental illness, in particular psychosis and schizophrenia. Certain studies suggest that cannabis accounts for 8–14% of schizophrenia cases, however, the presence of this link remains controversial. This article summarises the evidence supporting the relationship between cannabis and mental illness, with a focus on psychosis and schizophrenia, and the possible mechanisms at play. There is also a discussion of primary care management.