Substance Use and the Psychosis Spectrum

There is robust evidence that substance use is one of the most important modifiable risk factors for psychosis. Particularly, cannabis use has been consistently associated with different ends of the psychosis spectrum: from milder ends as subthreshold psychotic experiences to the most severe end as schizophrenia. Recent studies have reported different odds associated with different formulations of cannabis (i.e. low potency and high potency). Other well-known substances (opioids, stimulants, LSD, ketamine, inhalants etc.) and novel substances have also been associated with the psychosis spectrum, although the evidence is less robust. Finally, excessive alcohol use has been associated with the risk of psychosis in some studies. However, results to date have some discrepancies preventing to draw certain conclusions.

Excessive alcohol and substance use rates have trends of increase throughout the world. Furthermore, legalization of cannabis is currently discussed in different regions of the world. Interventions for excessive alcohol and substance use have great potential for primary, secondary and tertiary prevention of psychosis. In the period of such hot debates, more evidence on the associations between cannabis, other substances, excessive alcohol use and the psychosis spectrum, as well as on the effect of interventions for alcohol-substance use on psychosis risk, is urgently needed to promote individual and public mental health.

Alcohol-substance use may be an excellent target for indicated and selective prevention strategies as well as interventions for patients with an existing psychotic disorder. However, further studies are needed to tackle some issues. First, there are some concerns about the causality of the associations as the associations might partly be related to self-medication. Second, more evidence is needed on the associations with different domains of psychosis (i.e. positive, negative, disorganization and affective). Third, less evidence is available on the effect of interventions for alcohol-substance use on the risk of psychosis. Forth, evidence on the associations with the subthreshold end of the psychosis spectrum is less robust. Fifth, the evidence on the associations with the excessive alcohol use in different countries and cultures are contradictory. Sixth, despite more robust evidence on the associations with cannabis, evidence on the associations with other substances, as well as the differential effect of various types of substances is less robust. Finally, evidence on the associations between novel substances and the psychosis spectrum is lacking.

• The associations between different substances and the different domains of psychosis (i.e. positive, negative, disorganization and affective)
• The associations between excessive alcohol-substance use and subthreshold psychotic experiences/ high risk for psychosis groups
• The effects of interventions for alcohol-substance use on the course of psychotic symptoms (both in patients with psychotic disorders and in high risk for psychosis groups)
• The differential associations between different types of substances and the psychosis spectrum
• The associations between novel substances and the different ends of the psychosis spectrum
• Associations between alcohol use and the different ends of the psychosis spectrum
• Epidemiological data linking alcohol-substance use and the psychosis spectrum.

All kinds of research linking alcohol-substance use and psychosis (original articles, reviews, reports of original cases) are welcome.