Discussing the concept of substance-induced psychosis (SIP).

Substance-induced psychosis (SIP) is characterized by both substance use and a psychotic state, and it is assumed that the first causes the latter. In ICD-10 the diagnosis is categorized as and grouped together with substance use disorders, and to a large extent also treated as such in the health care system. Though criticism of the diagnostic construct of SIP dates back several decades, numerous large and high-quality studies have been published during the past 5-10 years that substantiate and amplify this critique. The way we understand SIP and even how we name it is of major importance for treatment and it has judicial consequences. It has been demonstrated that substance use alone is not sufficient to cause psychosis, and that other risk factors besides substance use are at play. These are risk factors that are also known to be associated with schizophrenia spectrum disorders. Furthermore, register-based studies from several different countries find that a large proportion, around one in four, of those who are initially diagnosed with an SIP over time are subsequently diagnosed with a schizophrenia spectrum disorder. This scoping review discusses the construct validity of SIP considering recent evidence. We challenge the immanent causal assumption in SIP, and advocate that the condition shares many features with the schizophrenia spectrum disorders. In conclusion, we argue that SIP just as well could be considered a first-episode psychotic disorder in patients with substance use.

Tidligere kriminalitet og psykisk helsehjelp hos personer med soningserfaring som blir dømt til tvungent psykisk helsevern.

Background: In the period 2002-2020, a total of 431 people were sentenced to coercive mental health care. Many of these had served time in prison, either previously or in connection with the criminal acts that led to the current sentences. This study examines the background, criminal history and mental health status of individuals before they committed the offences that led to their imprisonment. Material and method: Data from the Norwegian Correctional Service's Register of Imprisonments, the Register of Convictions, the Norwegian Patient Registry and Statistics Norway were used to study former prisoners who were sentenced to coercive mental health care in the period 2002-2020, who had served prison terms. Results: Among 286 former prisoners who were sentenced to coercive mental health care, 246 (86.0 %) had previous convictions, and 140 (49.0 %) had previously had criminal charges dropped due to doubt as to criminal culpability. Previous psychiatric illness in the last two years was studied in 186 individuals. Of these, 151 (81.2 %) had undergone treatment in the mental health service, with psychotic disorders (106/186 (57.0 %)) and substance use disorders (109/186 (58.6 %)) being the most common diagnoses. Interpretation: Former prisoners who are sentenced to coercive mental health care tend to have an extensive criminal and mental health care history prior to committing criminal acts that lead to coercive mental health care.

Annual incidence of substance-induced psychoses in Scandinavia from 2000 to 2016.

BACKGROUND: Substance-induced psychosis (SIP) is a serious condition and may predispose for schizophrenia. We know too little about SIP incidence over time and across countries, including substance-specific SIPs. We estimated annual incidence rate of SIP in Denmark, Norway, and Sweden according to substance, age, gender, and socioeconomic background. METHODS: Data were drawn from registries covering the whole adult population in the countries. Annual incidence rate per 100 000 persons of SIPs was estimated for Denmark and Sweden from 2000 to 2016 and for Norway from 2010 to 2015. RESULTS: The annual incidence rate of any SIP fluctuated between 9.3 and 14.1. The most commonly occurring SIPs were those induced by alcohol, cannabis, amphetamines, and multiple substances. There was a steady decrease in the incidence rate of alcohol-induced psychosis from the first to the last year of the observation period in Denmark (from 4.9 to 1.5) and Sweden (from 4.5 to 2.2). The incidence rate of cannabis-induced psychosis increased in all countries, from 2.6 to 5.6 in Denmark, from 0.8 to 2.7 in Sweden, and from 1.8 to 3.0 in Norway. Median age of any SIP decreased in Denmark (from 36 to 29 years) and Sweden (from 41 to 31 years). Incidence rates were higher in men and in individuals on disability pension, and increased more among those with high parental education. CONCLUSIONS: We found similar and stable incidence rates of any SIP in all Scandinavian countries through the observation period. The incidence of alcohol-induced psychosis decreased. The incidence of cannabis-induced psychosis increased.

[Poor uptake of service provision at a drug-related emergency department ­ a qualitative study]. / Ubenyttet behandlingstilbud ved rusakuttmottak ­ en kvalitativ studie.

BACKGROUND: The patient pathway for follow-up after a drug overdose, which is an important part of Norway's national overdose strategy, started up on 1 January 2022. Four years earlier, a collaboration was initiated between the ambulance service and the drug-related emergency department at Oslo University Hospital with the same aim as this patient pathway: to provide emergency follow-up in the specialist health service after a drug overdose. Uptake of the follow-up provision was minimal, and the purpose of this study was to investigate the reasons behind this. MATERIAL AND METHOD: We used a case study design and carried out twelve qualitative interviews with representatives from the ambulance service, the drug-related emergency department and the service user group. A thematic analysis of the interviews was then conducted. RESULTS: The analysis revealed five thematic areas with different explanations for the poor uptake of the service provision. There was insufficient information about the provision, and the admission criteria were unclear. Communication issues between the ambulance service and the drug-related emergency department meant that the provision did not function as an emergency service. The service users' wishes after an overdose did not correspond fully with the provision, and uptake was sometimes associated with sanctions. INTERPRETATION: The results show that things could have been done differently at a local level, but also that the content of the patient pathway is unclear, and that general guidelines can lead to the provision being perceived as unsafe. The knowledge generated from this survey can help uncover areas that require improvement at a national level in the follow-up pathway after a drug overdose.

Smoking in early adulthood is prospectively associated with prescriptions of antipsychotics, mood stabilizers, antidepressants and anxiolytics.

BACKGROUND: Whether smoking should be regarded as a risk factor for mental disorders remains unresolved. Prescribed psychotropic drugs can be used as indications for mental disorders. We investigated how smoking was prospectively related to prescription of antipsychotics, mood stabilizers, antidepressants, and anxiolytics. METHODS: Information about smoking, including the Fagerström Test for Nicotine Dependence, and relevant confounders, were obtained from the population-based Young in Norway Study (N = 2602), with four data collection waves between 1992 and 2006. These survey data were linked with information on prescriptions for psychotropic drugs from the comprehensive, nationwide Norwegian Prescription Database from 2007 to 2015. RESULTS: Daily smoking with high dependence in 2006 at age 28.5 (s.d. = 2.0) was associated with filling prescriptions of antipsychotics (OR, 6.57, 95% CI 2.19-19.70, p = 0.001), mood stabilizers (OR, 7.11, 95% CI 2.51-20.15, p < 0.001) and antidepressants (OR, 1.91, 95% CI 1.13-3.23, p = 0.016) 1-9 years later. Associations remained significant after adjustment for a variety of potential confounders measured before the assessment of smoking, including sociodemographic background, conduct problems, cannabis use, mental distress, and previous prescriptions for psychotropic medications. The association between smoking and prescription of anxiolytics was weaker and more unstable. CONCLUSIONS: In this study of young adults, daily smoking with high dependence was associated with later prescriptions of antipsychotics, mood stabilizers and antidepressants, indicating smoking as a risk factor for mental disorders treated with these drugs.

Concentrations of psychoactive substances in blood samples from non-fatal and fatal opioid overdoses.

AIM: The primary aim was to compare concentrations of psychoactive substances in blood in non-fatal and fatal opioid overdoses. The secondary aim was to assess the concentration levels of naloxone in blood in non-fatal overdoses and the association between naloxone findings and concomitantly detected drugs. METHOD DESIGN: Case-control study. SETTING: Norway. Fatal overdoses from 2017 and non-fatal overdoses from February 2018 to September 2019. CASES: Thirty-one non-fatal and 160 fatal opioid overdose cases. Data from the non-fatal overdoses were collected from hospital records and blood samples, and data from the fatal overdoses were collected from autopsy reports. Concentrations of psychoactive substances (including ethanol) in blood samples were collected at the time of hospital admission for the non-fatal overdoses and during autopsy for the fatal overdoses. RESULTS: The median number of different substances detected was four for fatal and five for non-fatal overdoses. The fatal overdoses had higher pooled concentrations of opioids (188 vs 57.2 ng/mL, P < .001), benzodiazepines (5467 vs 2051 ng/mL, P = .005) and amphetamines (581 vs 121 ng/mL, P < .001) than the non-fatal overdoses. A linear relationship between naloxone and concomitant pooled opioid concentrations was found (95% confidence interval = 0.002-0.135, P < .05). CONCLUSION: The total load of drug concentrations was associated with the fatal outcome of an overdose, while the number of drugs used, to a lesser extent, differentiated between those who survived and those who died from an overdose. Higher opioid concentrations were associated with treatment with higher naloxone doses.

Cannabis use in early adulthood is prospectively associated with prescriptions of antipsychotics, mood stabilizers, and antidepressants.

OBJECTIVE: Cannabis is an acknowledged risk factor for some mental disorders, but for others the evidence is inconclusive. Prescribed medicinal drugs can be used as proxies for mental disorders. In this study, we investigate how use of cannabis is prospectively related to prescription of antipsychotics, mood stabilizers, antidepressants, and anxiolytics. METHODS: Data on cannabis exposure and relevant confounders were obtained from 2,602 individuals in the longitudinal Young in Norway Study, providing survey data from four data collection waves between 1992 and 2006. Data were coupled with information about prescriptions for psychotropic drugs from the Norwegian Prescription Database between 2007 and 2015. RESULTS: Past year cannabis use increased the risk of prescription of antipsychotics (OR = 5.56, 95 % CI 1.64 - 18.87), mood stabilizers (OR = 5.36, 95 % CI 1.99 - 14.44) and antidepressants (OR = 2.10, 95 % CI 1.36 - 3.25), after accounting for sociodemographic variables, conduct problems, additional drug use, mental distress, and prescriptions the year before cannabis use was measured. CONCLUSIONS: In this study of young adults from the general population, past year cannabis use was associated with later prescriptions of antipsychotics, mood stabilizers, and antidepressants.

Amphetamine-induced psychosis: Transition to schizophrenia and mortality in a small prospective sample.

BACKGROUND AND OBJECTIVES: We investigated transition from amphetamine-induced psychosis (AIP) to schizophrenia. METHODS: A sample of 28 individuals was identified while hospitalized for AIP. We reviewed their hospital records after six years. RESULTS: During follow-up, seven individuals (25%) died and nine (32%) had moved from the area. Of the remaining 12, four individuals (25%) were diagnosed with schizophrenia. These individuals were, at baseline, characterized by fewer hallucinatory symptoms and more homelessness. CONCLUSION AND SCIENTIFIC SIGNIFICANCE: Hospitalization for AIP was a relatively specific risk factor for schizophrenia and the mortality rate in AIP was high.

Loneliness in adolescence and prescription of psychotropic drugs in adulthood: 23-year longitudinal population-based and registry study.

BACKGROUND: The role of adolescent loneliness in adult mental health and prescriptions of psychotropic drugs remains underexplored. AIMS: We aim to determine whether (a) experiencing loneliness in adolescence and (b) changes in loneliness from adolescence to adulthood are prospectively associated with prescriptions for a variety of psychotropic drugs in adulthood. METHOD: We used data from a Norwegian population-based sample with 2602 participants, collected across four waves between 1992 and 2006. Loneliness was assessed at each wave, with survey data linked to medicinal drug prescription records from the Norwegian Prescription Database. We identified prescription histories of antipsychotics, mood stabilisers, antidepressants and benzodiazepines from 2007 to 2015, for each participant. We use latent growth curve analyses to model the relationship of adolescent loneliness and loneliness change from adolescence to adulthood, with subsequent psychotropic drugs prescription. RESULTS: Adolescents with heightened loneliness, and adolescents whose loneliness increased into young adulthood, had a greater likelihood of being prescribed antipsychotics, mood stabilisers and antidepressants in adulthood. These associations remained significant after adjustment for confounders such as sociodemographic characteristics, conduct problems, substance use and mental health problems. CONCLUSIONS: Loneliness in adolescence and its adverse development over a span of 15 years was linked to higher risk of receiving prescriptions for antipsychotics, mood stabilisers and antidepressants later in life. The findings may indicate that loneliness increases the risk for developing psychotic disorders, bipolar disorders and major depression.

The effect of employment support integrated in substance use treatment: A health economic cost-effectiveness simulation of three different interventions.

Background: Unemployment rates for individuals in treatment for substance use disorder (SUD) are high, with Norwegian estimates in the range of 81%-89%. Although Individual Placement and Support (IPS) represents a promising method to improved vocational outcome, cross-disciplinary investigations are needed to document implementation benefits and address reimbursements needs. The aim of this study was to model the potential socioeconomic value of employment support integrated in SUD treatment. Methods: Based on scientific publications, an ongoing randomised controlled trial (RCT) on employment support integrated in SUD treatment, and publicly available economy data, we made qualified assumptions about costs and socioeconomic gain for the different interventions targeting employment for patients with SUD: (1) treatment as usual (TAU); (2) TAU and a self-help guide and a workshop; and (3) TAU and IPS. For each intervention, we simulated three different outcome scenarios based on 100 patients. Results: Assuming a 40% employment rate and full-time employment (100%) for 10 years following IPS, we found a 10-year socioeconomic effect of €18,732,146. The corresponding effect for the more conservative TAU + IPS simulation assuming 40% part-time positions (25%) for five years, was €2,519,906. Compared to the two alternative interventions, IPS was cost-effective and more beneficial after six months to two years. Discussion: This concept evaluation study suggests that integrating employment support in the health services is socioeconomically beneficial. Our finding is relevant for decision makers within politics and health. Once employment rates from our ongoing RCT is available, real-life data will be applied to adjust model assumptions and socioeconomic value assumptions.

Amphetamine-induced psychosis--a separate diagnostic entity or primary psychosis triggered in the vulnerable?

Use of amphetamine and methamphetamine is widespread in the general population and common among patients with psychiatric disorders. Amphetamines may induce symptoms of psychosis very similar to those of acute schizophrenia spectrum psychosis. This has been an argument for using amphetamine-induced psychosis as a model for primary psychotic disorders. To distinguish the two types of psychosis on the basis of acute symptoms is difficult. However, acute psychosis induced by amphetamines seems to have a faster recovery and appears to resolve more completely compared to schizophrenic psychosis. The increased vulnerability for acute amphetamine induced psychosis seen among those with schizophrenia, schizotypal personality and, to a certain degree other psychiatric disorders, is also shared by non-psychiatric individuals who previously have experienced amphetamine-induced psychosis. Schizophrenia spectrum disorder and amphetamine-induced psychosis are further linked together by the finding of several susceptibility genes common to both conditions. These genes probably lower the threshold for becoming psychotic and increase the risk for a poorer clinical course of the disease.The complex relationship between amphetamine use and psychosis has received much attention but is still not adequately explored. Our paper reviews the literature in this field and proposes a stress-vulnerability model for understanding the relationship between amphetamine use and psychosis.

PriSUD-Nordic-Diagnosing and Treating Substance Use Disorders in the Prison Population: Protocol for a Mixed Methods Study.

BACKGROUND: A large proportion of the prison population experiences substance use disorders (SUDs), which are associated with poor physical and mental health, social marginalization, and economic disadvantage. Despite the global situation characterized by the incarceration of large numbers of people with SUD and the health problems associated with SUD, people in prison are underrepresented in public health research. OBJECTIVE: The overall objective of the PriSUD (Diagnosing and Treating Substance Use Disorders in Prison)-Nordic project is to develop new knowledge that will contribute to better mental and physical health, improved quality of life, and better life expectancies among people with SUD in prison. METHODS: PriSUD-Nordic is based on a multidisciplinary mixed method approach, including the methodological perspectives of both quantitative and qualitative methods. The qualitative part includes ethnographic fieldwork and semistructured interviews. The quantitative part is a registry-based cohort study including national registry data from Norway, Denmark, and Sweden. The national prison cohorts will comprise approximately 500,000 individuals and include all people imprisoned in Norway, Sweden, and Demark during the period from 2000 to 2019. The project will investigate the prison population during three different time periods: before imprisonment, during imprisonment, and after release. RESULTS: PriSUD-Nordic was funded by The Research Council of Norway in December 2019, and funding started in 2020. Data collection is ongoing and will be completed in the first quarter of 2022. Data will be analyzed in spring 2022 and the results will be disseminated in 2022-2023. The PriSUD-Nordic project has formal ethical approval related to all work packages. CONCLUSIONS: PriSUD-Nordic will be the first research project to investigate the epidemiology and the lived experiences of people with SUD in the Nordic prison population. Successful research in this field will have the potential to identify significant areas of benefit and will have important implications for ongoing policy related to interventions for SUD in the prison population. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/35182.

The effect evaluation of Individual Placement and Support (IPS) for patients with substance use disorders: study protocol for a randomized controlled trial of IPS versus enhanced self-help.

BACKGROUND: Employment is associated with better outcomes of substance use treatment and protects against relapse after treatment completion. Unemployment rates are high for people with substance use disorders (SUD) who undergo treatment, with Norwegian estimates ranging from 81 to 91%. Evidence-based vocational models are lacking for patients in SUD treatment but exist for patients with psychosis in terms of Individual Placement and Support (IPS). The aim of the IPS for substance use disorders (IPS-SUD) trial is to investigate the effect of IPS in a SUD population. METHODS/DESIGN: The IPS-SUD trial is a randomized controlled trial (RCT) comparing IPS to an enhanced control intervention. The study is a seven-site, two-arm, pragmatic, parallel-group, superiority RCT. Participants are randomly assigned (1:1) to receive either IPS plus treatment as usual (TAU) or to receive a self-help guide book and 12-h workshop plus 1-h individual vocational guidance plus TAU. Aiming to recruit 200 participants, we will be able to detect a 20% difference in the main outcome of employment with 90% power. We will make assessments at inclusion and at 6- and 12-month follow-ups and obtain outcome data on employment from national mandatory registries. The primary outcome will be at least 1 day of competitive employment during the 18-month follow-up period. Secondary employment outcomes will capture the pattern and extent of employment in terms of total time worked (days/hours), time to first employment, number of different jobs, duration of the longest employment, and sustained employment. Secondary non-employment outcomes will be substance use, mental distress, and quality of life measured by validated instruments at 6, 12, and 18 months follow-up assessments. To be eligible, participants must be between 18 and 65 years, currently unemployed and in treatment for SUD. DISCUSSION: The IPS-SUD trial will provide evidence for the use of IPS in a SUD population. Findings from the study will have implications for service delivery. TRIAL REGISTRATION: ClinicalTrials.gov NCT04289415 . Registered on February 28, 2020.

Use of anabolic-androgenic steroids and other substances prior to and during imprisonment - Results from the Norwegian Offender Mental Health and Addiction (NorMA) study.

BACKGROUND: Anabolic-androgenic steroid (AAS) use is associated with health problems and substance use. Substance use is common among inmates. This study aims to estimate lifetime and prison use of AAS and other substances, compare characteristics of groups of inmates, and describe factors associated with AAS use in a national prison population. METHODS: Data from the Norwegian Offender Mental Health and Addiction (NorMA) Study, a cross-sectional survey of people in prisons, included sociodemographic variables and lifetime and prison use of AAS and other substances. Altogether 1,499 inmates, including 96 (6.4%) women, were divided into three mutually exclusive groups according to lifetime AAS use, non-AAS substance use and no substance use. RESULTS: Lifetime AAS use was reported by 427 (28.5%) inmates; 6 women and 421 men. Non-AAS substance use was reported by 593 (39.6%) and 479 (31.9%) had never used AAS or non-AAS substances. Compared to the non-AAS substance group, the AAS group reported younger debut ages for nearly all non-AAS substances, higher mean number of non-AAS substances used in their lifetime (8.9, 6.6, p < 0.001), during the six months prior to incarceration (5.2, 3.1, p < 0.001), and during (2.3, 1.3, p < 0.001) imprisonment. Although 120 (8.0%) inmates used AAS during the six months prior to incarceration, only ten continued during imprisonment. CONCLUSIONS: Lifetime AAS use is common among inmates and may be an indicator of more severe substance use problems. Screening for previous and present AAS use at incarceration and increased staff awareness are needed to tailor treatment approaches appropriately.

Factors associated with drug use in prison - results from the Norwegian offender mental health and addiction (NorMA) study.

BACKGROUND: Remarkably little is known about drug use during imprisonment, including whether it represents a continuation of pre-incarceration drug use, or whether prison is also a setting for drug use initiation. This paper aims to describe drug use among people in prison in Norway and investigate risk factors associated with in-prison drug use. METHODS: We used data from the Norwegian Offender Mental Health and Addiction (NorMA) Study, a cross-sectional survey of 1499 individuals in Norwegian prisons. Respondents reported on drug use (narcotics and non-prescribed medications) both before and during imprisonment. We used multivariate logistic regression to investigate the associations between drug use in prison and demographics, previous drug use, mental health, and criminal activity. RESULTS: Sixty-five percent of respondents reported lifetime drug use, and about 50% reported daily use of drugs during the 6 months before incarceration. Thirty-five percent reported ever using drugs in prison, but initiation of drug used during incarceration was uncommon. In a multivariate model, factors independently associated with drug use in prison included lifetime number of drugs used (adjusted odds ratio [aOR] = 1.17; 95% confidence interval [CI] 1.12-1.23; p <  0.001), daily drug use in the 6 months before imprisonment (aOR = 7.12; 95%CI 3.99-12.70; p <  0.001), and being intoxicated while committing the crime related to current imprisonment (aOR = 2.13; 95%CI 1.13-4.03; p = 0.020). CONCLUSIONS: In-prison drug use is independently associated with high-risk drug use before imprisonment. To reduce drug use in prison, correctional services must systematically screen for pre-prison drug use and offer effective drug treatment for those in need.

Inmates with Harmful Substance Use Increase Both Exercise and Nicotine Use Under Incarceration.

Exercise is increasingly understood as an important resource for people who engage in harmful substance use, including those in prison. Little is known about how inmates adopt various health behaviors during incarceration, without interventions. This cross-sectional study analyzed self-reports from 1464 inmates in Norwegian prisons in 2013⁻2014, compared them according to harmful substance use pre-incarceration, and explored changes in exercise and nicotine use during incarceration. Results were presented in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. Inmates with harmful substance use reported higher rates of smoking, smokeless tobacco, and physical inactivity pre-incarceration than inmates without harmful use. However, inmates with harmful use also exhibited more behavioral changes: they adopted exercise, ceased smoking, and adopted smokeless tobacco at higher rates during incarceration than the non-harmful group, to the extent that inmates with harmful use exercised during incarceration more. Exercise is being taken up by a significant proportion of inmates, and may in particular be a replacement behavior for substance use. However, unhealthy behaviors also begin or are maintained. If prisons were used as an arena to facilitate healthy behaviors, the public health benefits to a marginalized group such as substance-using inmates could be substantial.

Substance use and sociodemographic background as risk factors for lifetime psychotic experiences in a non-clinical sample.

INTRODUCTION: Psychotic experiences (PE) are relatively common in the general population. PE is associated with mental health impairment and may be predictive of clinical psychosis. Substance use predicts PE, but the association is insufficiently understood, particularly the role of illicit substances. The purpose of this study was to describe PE (visual and auditory hallucinations and delusions of reference and persecution) in a population characterized by high levels of substance use and to investigate substance use and sociodemographic background characteristics as risk factors for PE. METHODS: We used data from the Norwegian Offender Mental Health and Addiction Study (NorMA), a cross-sectional survey of 1499 individuals from Norwegian prisons. The outcome was one, two, three or four types of PE during the lifetime. The association between different variables and PE was investigated using multinomial logistic regression with three outcome categories: 0 PE, 1-2 PE and 3-4 PE. RESULTS: The prevalence of lifetime PE was 53.7%. Several substances were strongly associated with PE: For cannabis, the adjusted relative risk ratio (RRR) of 1-2 PE was 2.78 (95% CI 1.89-4.10) and of 3-4 PE it was 4.36 (2.58-7.36). For amphetamine, the RRR of 1-2 PE was 3.26 (2.11-5.05) and of 3-4 PE it was 5.93 (3.72-9.46). For all variables, the association to PE was stronger with more types of PE. CONCLUSIONS: High levels of alcohol use, and lifetime use of cannabis, amphetamine and heroin were associated with PE. These effects were robust even when the substance use variables were adjusted against each other. This research received no specific grant from any funding agency, commercial or not-for-profit sectors.

Long-term risk factors for substance-induced and primary psychosis after release from prison. A longitudinal study of substance users.

PURPOSE: The purpose of this study was to determine long-term risk factors for substance-induced and primary psychosis after release from prison. MATERIAL: We used a longitudinal register-based cohort study combining European version of Addiction Severity Index (Europ-ASI) interviews and the Swedish inpatient register. The study included 6217 individuals who were in the Swedish criminal justice system from 2001 to 2006. MEASUREMENTS: The outcomes were substance-induced and primary psychosis as defined by the International Classification of Disease - 10th version. All variables for estimating baseline risk were drawn from the Europ-ASI interview, and included information on substance use, demographics and health. The interview database and the inpatient register were coupled, and groups were compared by using tests of significance and logistic regression. RESULTS: Polydrug use was the strongest predictor for substance induced psychosis (OR=9.55, 95% CI 3.42-26.67), but all substances imposed an increased risk. Previous psychiatric hospitalization and non-drug related hallucinations were significant, but weaker, risk factors. The only substance variable that predicted primary psychosis was cannabis (OR=2.62, 95% CI 1.39-4.96), but previous psychiatric hospitalization (OR=3.22, 95% CI 2.27-4.54) and non-drug related hallucinations (OR=4.00, 95% CI 2.82-5.67) were even stronger predictors. CONCLUSIONS: Cannabis use was a risk factor for primary psychosis, but other health related individual risk factors were even more important. Polydrug use was the strongest risk factor for substance-induced psychosis.