We examined whether cannabis use contributes to the increased risk of psychotic disorder for non-western minorities in Europe.

We used data from the EU-GEI study (collected at sites in Spain, Italy, France, the United Kingdom, and the Netherlands) on 825 first-episode patients and 1026 controls. We estimated the odds ratio (OR) of psychotic disorder for several groups of migrants compared with the local reference population, without and with adjustment for measures of cannabis use.

The OR of psychotic disorder for non-western minorities, adjusted for age, sex, and recruitment area, was 1.80 (95% CI 1.39–2.33). Further adjustment of this OR for frequency of cannabis use had a minimal effect: OR = 1.81 (95% CI 1.38–2.37). The same applied to adjustment for frequency of use of high-potency cannabis. Likewise, adjustments of ORs for most sub-groups of non-western countries had a minimal effect. There were two exceptions. For the Black Caribbean group in London, after adjustment for frequency of use of high-potency cannabis the OR decreased from 2.45 (95% CI 1.25–4.79) to 1.61 (95% CI 0.74–3.51). Similarly, the OR for Surinamese and Dutch Antillean individuals in Amsterdam decreased after adjustment for daily use: from 2.57 (95% CI 1.07–6.15) to 1.67 (95% CI 0.62–4.53).

The contribution of cannabis use to the excess risk of psychotic disorder for non-western minorities was small. However, some evidence of an effect was found for people of Black Caribbean heritage in London and for those of Surinamese and Dutch Antillean heritage in Amsterdam.

Gene x environment (G×E) interactions, i.e. genetic modulation of the sensitivity to environmental factors and/or environmental control of the gene expression, have not been reliably established regarding aetiology of psychotic disorders. Moreover, recent studies have shown associations between the polygenic risk scores for schizophrenia (PRS-SZ) and some risk factors of psychotic disorders, challenging the traditional gene v. environment dichotomy. In the present article, we studied the role of GxE interaction between psychosocial stressors (childhood trauma, stressful life-events, self-reported discrimination experiences and low social capital) and the PRS-SZ on subclinical psychosis in a population-based sample.

Data were drawn from the EUropean network of national schizophrenia networks studying Gene-Environment Interactions (EU-GEI) study, in which subjects without psychotic disorders were included in six countries. The sample was restricted to European descendant subjects (n = 706). Subclinical dimensions of psychosis (positive, negative, and depressive) were measured by the Community Assessment of Psychic Experiences (CAPE) scale. Associations between the PRS-SZ and the psychosocial stressors were tested. For each dimension, the interactions between genes and environment were assessed using linear models and comparing explained variances of ‘Genetic’ models (solely fitted with PRS-SZ), ‘Environmental’ models (solely fitted with each environmental stressor), ‘Independent’ models (with PRS-SZ and each environmental factor), and ‘Interaction’ models (Independent models plus an interaction term between the PRS-SZ and each environmental factor). Likelihood ration tests (LRT) compared the fit of the different models.

There were no genes-environment associations. PRS-SZ was associated with positive dimensions (β = 0.092, R2 = 7.50%), and most psychosocial stressors were associated with all three subclinical psychotic dimensions (except social capital and positive dimension). Concerning the positive dimension, Independent models fitted better than Environmental and Genetic models. No significant GxE interaction was observed for any dimension.

This study in subjects without psychotic disorders suggests that (i) the aetiological continuum hypothesis could concern particularly the positive dimension of subclinical psychosis, (ii) genetic and environmental factors have independent effects on the level of this positive dimension, (iii) and that interactions between genetic and individual environmental factors could not be identified in this sample.

The social defeat hypothesis of psychosis posits that an outsider status or subordinate position is a common denominator of several psychosis risk factors, leads to elevated striatal dopamine function and thereby to an increased risk for the disorder. The purpose of this paper is to examine whether this hypothesis offers a good explanation for the increased psychosis risk for migrants from developing countries. Method: Review of literature. Results: The outsider status and subordinate position of many migrants from developing countries in Europe, and of Africans in particular, is evident. It is also clear that racism contributes to this situation. An interpretation of racism as psychotogenic is supported by findings of increased risks for other discriminated groups, such as homosexuals, individuals with a low IQ or a hearing impairment. The single study that examined dopamine function in migrants reported indeed elevated stress-induced dopamine release and dopamine synthesis capacity (Egerton et al., 2017). Recently, we examined the time course of the RR of treatment for psychosis for all migrants to the Netherlands (Termorshuizen & Selten, submitted). Contrary to our expectations, the RR for migrants from sub-Saharan Africa was already increased in the year of arrival (RR=2.5; 2.0-3.1), particularly for those aged 10-20 years (RR=6.1; 2.9-12.6). Conclusion: The social defeat hypothesis accords well with a psychotogenic effect of racism, but replications of the dopamine study are needed. The finding of an increased risk for Africans in the year of arrival suggests that racism is not the single cause of their increased risk.

No significant relationships.

Recovery in psychotic disorders is a concept that evolved through the last decades. Thanks to the contribution of different researchers, together with the recovery movement, a switch happened from a service-based to a client-based approach towards recovery. The Dutch framework considers recovery as the interplay of symptomatic, personal, functional and societal aspects, determined by different biological, psychological, personal and social factors. Literature on this fourdimensional perspective is still scarce. In addition, even if an increased incidence of psychotic disorders has been recognized in ethnic minority populations and migrants, studies on the influence of ethnicity and migration on recovery in psychotic disorders is limited.

To write a systematic literature review on how ethnic minority status and migration history may affect symptomatic, personal, functional and societal recovery.

A systematic search of the main databases, followed by a four-step selection process to include studies comparing migrants or ethnic minority populations and the non-minoritarian/autochthonous population in terms of recovery. A qualitative, narrative summary has been performed.

Thirty-eight articles have been included. Literature is heterogeneous, focused on clinical outcomes and mostly based on data from the UK and the USA. As a common thread, ethnic minority status and migration history result to negatively influence societal, personal and, to a lower extent, clinical recovery.

Further studies based in different cultural backgrounds and focused on recovery in its multiple aspects are needed, to get a better understanding of the contextual and structural factors that affect the interaction between ethnicity, migration and recovery in psychotic disorders.

No significant relationships.

Impaired mentalizing ability – an impaired ability to understand one's own and other people's behavior in terms of mental states – is associated with social dysfunction in non-affective psychotic disorder (NAPD). We tested whether adding mentalization-based treatment for psychotic disorder (MBTp) to treatment as usual (TAU) results in greater improvement in social functioning.

Multicenter, rater-blinded, randomized controlled trial. Eighty-four patients with NAPD were assigned to TAU or MBTp plus TAU. Patients in the MBTp group received 18 months of MBTp, consisting of weekly group sessions and one individual session per 2 weeks. Social functioning was measured using the Social Functioning Scale. We conducted ANCOVAs to examine the difference between treatment conditions directly after treatment and at 6-month follow-up and performed moderation and mediation analyses.

Intention-to-treat analyses showed no significant differences between groups post-treatment (p = 0.31) but revealed the MBTp group to be superior to TAU at follow-up (p = 0.03). Patients in the MBTp group also seemed to perform better on measures of mentalizing ability, although evidence of a mediation effect was limited (p = 0.06). Lastly, MBTp treatment was less effective in chronic patients than in recent-onset patients (p = 0.049) and overall symptoms at baseline were mild, which may have reduced the overall effectiveness of the intervention.

The results suggest that MBTp plus TAU may lead to more robust improvements in social functioning compared to TAU, especially for patients with a recent onset of psychosis.

To estimate the risk of developing autism-spectrum disorder (ASD) in children born to immigrants as compared to children of Dutch-born parents.

Retrospective, population-based cohort study of all live births (N= 106,953) between 1998 and 2007 in a circumscribed geographical region in the Netherlands. Cohort members were linked to the Psychiatric Case Register to identify diagnosed cases.

518 cases of ASD were identified, including 150 children with autism and 368 children with Asperger syndrome or PDD-NOS. Children born to migrants from developing countries were at significantly lower risk of ASD (rate ratio (RR)= 0.6, 95% (CI) 0.5-0.9) than children of Dutch-born parents. Within the ASD group, the risk for the subgroup with Asperger syndrome and PDD-NOS was reduced (RR= 0.4, 95% CI 0.3-0.6), whereas that for narrowly defined autism was nonsignificantly increased (RR= 1.4, 95% CI 0.9-2.4). Migrant groups did not differ in age at diagnosis.

The results echo Swedish findings indicating a reversal of risk gradient in children of parents from developing countries, specifically a decreased risk for high-functioning and increased risk for low-functioning autism.

Individuals with autism spectrum disorder (ASD) appear to be at increased risk of non-affective psychotic disorder (NAPD) and bipolar disorder (BD). However, most previous studies examined the co-occurrence of ASD and NAPD or BD, ignoring possible diagnostic bias and selection bias. We used longitudinal data from Dutch psychiatric case registers to assess the risk of NAPD or BD among individuals with ASD, and compared the results to those obtained for the Dutch population in earlier studies.

Individuals with ASD (n = 17 234) were followed up between 16 and 35 years of age. Kaplan–Meier estimates were used to calculate the risk of NAPD or BD. We conducted separate analyses to reduce possible bias, including an analysis among individuals diagnosed with ASD before age 16 years (n = 8337).

Of the individuals with ASD, 23.50% (95% confidence interval 21.87–25.22) were diagnosed with NAPD and 3.79% (3.06–4.69) with BD before age 35 years. The corresponding figures for the general population were 0.91% (0.63–1.28) and 0.13% (0.08–0.20). Risk estimates were substantially lower, but still higher than general population estimates, when we restricted our analyses to individuals diagnosed with ASD before age 16, with 1.87% (1.33–2.61) being diagnosed with NAPD and 0.57% (0.21–1.53) with BD before age 25 years. The corresponding figures for the general population were 0.63% (0.44–0.86) and 0.08% (0.05–0.12).

Individuals with ASD are at increased risk of NAPD or BD. This is likely not the result of diagnostic or selection bias.

Minor stresses measured in daily life have repeatedly been associated with increased momentary psychotic experiences, both in individuals with psychotic disorders and in persons who are genetically at an increased risk for these disorders. Severe hearing impairment (SHI) is an environmental risk factor for psychotic disorder, possibly due to the experience of social exclusion. The aim of the current study is to investigate whether people with SHI exhibit higher levels of psychotic reactivity to social stressors in daily life than normal-hearing controls and whether this reactivity is associated with decreased baseline dopamine (DA) D2/3 receptor availability and/or elevated DA release following a dexamphetamine challenge.

We conducted an experience sampling study in 15 young adults with SHI and 19 matched normal-hearing controls who had previously participated in a single photon emission computed tomography study measuring DA D2/3 receptor availability and DA release in response to dexamphetamine.

The association between social stress and momentary psychotic experiences in daily life was stronger among SHI participants than among normal-hearing controls. Interactions between social stress and baseline striatal DA D2/3 receptor availability or DA release were not significant in multilevel models of momentary psychotic experiences including age, sex and tobacco use.

While both elevated striatal DA release and elevated psychotic stress reactivity have been found in the same population defined by an environmental risk factor, SHI, their inter-relationship cannot be established. Further research is warranted to clarify the association between biological and psychological endophenotypes and psychosis risk.

Environmental factors such as urban birth and ethnic minority position have been related to risk for psychotic disorders. There is some evidence that not only individual, but also neighborhood characteristics influence this risk. The aim of this study was to investigate social disorganization of neighborhoods and incidence of psychotic disorders.

The research was a 7-year first-contact incidence study of psychotic disorders in The Hague. Neighborhood characteristics included continuous, dichotomous and cumulative measures of socio-economic level, residential mobility, ethnic diversity, proportion of single person households, voter turnout, population density and crime level. Using multilevel Poisson regression analysis, incidence rate ratios (IRRs) and 95% confidence intervals (CIs) of psychotic disorders were calculated for the indicators of neighborhood social disorganization.

A total of 618 incident cases were identified. Neighborhood socio-economic level and residential mobility had the strongest association with incidence of psychotic disorders [individual-level adjusted Wald χ21 = 13.03 (p = 0.0003) and 5.51 (p = 0.02), respectively]. All but one (proportion of single person households) of the dichotomous neighborhood indicators were significantly associated with a higher IRR. The cumulative degree of neighborhood social disorganization was strongly and linearly associated with the incidence of psychotic disorders (trend test, Wald χ25 = 25.76, p = 0.0001). The IRR in neighborhoods with the highest degree of social disorganization was 1.95 (95% CI 1.38–2.75) compared with the lowest disorganization category.

The findings suggest that the risk for developing a psychotic disorder is higher for people living in socially disorganized environments. Longitudinal studies are needed to investigate causality.

The selection hypothesis posits that the increased rates of psychosis observed among migrants are due to selective migration of people who are predisposed to develop the disorder. To test this hypothesis, we examined whether risk factors for psychosis are more prevalent among future emigrants.

A cohort of 49 321 Swedish military conscripts was assessed at age 18 years on cannabis use, IQ, psychiatric diagnosis, social adjustment, history of trauma and urbanicity of place of upbringing. Through data linkage we examined whether these exposures predicted emigration out of Sweden. We also calculated the emigrants' hypothetical relative risk compared with non-emigrants for developing a non-affective psychotic disorder.

Low IQ [odds ratio (OR) 0.5, 95% confidence interval (95% CI) 0.3–0.9] and ‘poor social adjustment’ (OR 0.4, 95% CI 0.2–0.8) were significantly less prevalent among prospective emigrants, whereas a history of urban upbringing (OR 2.3, 95% CI 1.4–3.7) was significantly more common. Apart from a non-significant increase in cannabis use among emigrants (OR 1.6, 95% CI 0.8–3.1), there were no major group differences in any other risk factors. Compared to non-emigrants, hypothetical relative risks for developing non-affective psychotic disorder were 0.7 (95% CI 0.4–1.2) and 0.8 (95% CI 0.7–1.0), respectively, for emigrants narrowly and broadly defined.

This study adds to an increasing body of evidence opposing the selection hypothesis.

Ethnic minority position is associated with increased risk for psychotic outcomes, which may be mediated by experiences of social exclusion, defeat and discrimination. Sexual minorities are subject to similar stressors. The aim of this study is to examine whether sexual minorities are at increased risk for psychotic symptoms and to explore mediating pathways.

A cross-sectional survey was performed assessing cumulative incidence of psychotic symptoms with the Composite International Diagnostic Interview in two separate random general population samples (NEMESIS-1 and NEMESIS-2). Participants were sexually active and aged 18–64 years (n = 5927, n = 5308). Being lesbian, gay or bisexual (LGB) was defined as having sexual relations with at least one same-sex partner during the past year. Lifetime experience of any psychotic symptom was analysed using logistic regression, adjusted for gender, educational level, urbanicity, foreign-born parents, living without a partner, cannabis use and other drug use.

The rate of any psychotic symptom was elevated in the LGB population as compared with the heterosexual population both in NEMESIS-1 [odds ratio (OR) 2.56, 95% confidence interval (CI) 1.71–3.84] and NEMESIS-2 (OR 2.30, 95% CI 1.42–3.71). Childhood trauma, bullying and experience of discrimination partly mediated the association.

The finding that LGB orientation is associated with psychotic symptoms adds to the growing body of literature linking minority status with psychosis and other mental health problems, and suggests that exposure to minority stress represents an important mechanism.

Approximately 11% of schoolchildren are bullied on a regular basis. It has been argued that continuous exposure to stress is related to the development of psychotic symptoms. The current study sought to investigate whether being bullied in childhood is related to the development of psychotic symptoms.

A search of PubMed, PsycINFO and EMBASE was conducted. The reference lists of included papers were searched to identify other eligible papers. A meta-analysis was performed on a subgroup of studies.

We found four clinical and 10 general population studies that met inclusion criteria. The results of the clinical studies were mixed. However, the results of the non-clinical studies provided more consistent evidence that school bullying is related to the development of non-clinical psychotic symptoms. Stronger associations were found with increased frequency and severity and longer duration of being bullied. We performed a meta-analysis on seven population-based studies, yielding unadjusted and adjusted odds ratios (ORs) of 2.7 [95% confidence interval (CI) 2.1–3.6] and 2.3 (95% CI 1.5–3.4) respectively.

Although there is some evidence of an association between bullying and psychosis in clinical samples, the research is too sparse to draw any firm conclusions. However, population-based non-clinical studies support the role of bullying in the development of psychotic symptoms later in life. These findings are consistent with findings of an increased risk of psychotic symptoms among those exposed to other types of abuse.

Interventions to improve adherence to treatment in people with psychotic disorders have produced inconclusive results. We developed a new treatment, treatment adherence therapy (TAT), whose intervention modules are tailored to the reasons for an individual's non-adherence.

To examine the effectiveness of TAT with regard to service engagement and medication adherence in out-patients with psychotic disorders who engage poorly.

Randomised controlled study of TAT v. treatment as usual (TAU) in 109 out-patients. Most outcome measurements were performed by masked assessors. We used intention-to-treat multivariate analyses (Dutch Trial Registry: NTR1159).

Treatment adherence therapy v. TAU significantly benefited service engagement (Cohen's d = 0.48) and medication adherence (Cohen's d = 0.43). Results remained significant at 6-month follow-up for medication adherence. Near-significant effects were also found regarding involuntary readmissions (1.9% v. 11.8%, P = 0.053). Symptoms and quality of life did not improve.

Treatment adherence therapy helps improve engagement and adherence, and may prevent involuntary admission.

Psychotic disorders are more common in people from ethnic minorities. If psychosis exists as a continuous phenotype, ethnic disparities in psychotic disorder will be accompanied by similar ethnic disparities in the rate of psychotic symptoms. This study examined ethnic disparities in self-reported hallucinations in a population sample of young adults.

A cross-sectional population survey (n=2258) was carried out in the south-west Netherlands. Seven ethnic groups were delineated: Dutch natives, Turks, Moroccans, Surinamese/Antilleans, Indonesians, other non-Western immigrants (mostly from Africa or Asia) and Western immigrants (mostly from Western Europe). Self-reported auditory and visual hallucinations were assessed with the Adult Self-Report (ASR). Indicators of social adversity included social difficulties and a significant drop in financial resources.

Compared to Dutch natives, Turkish females [odds ratio (OR) 13.48, 95% confidence interval (CI) 5.97–30.42], Moroccan males (OR 8.36, 95% CI 3.29–21.22), Surinamese/Antilleans (OR 2.19, 95% CI 1.05–4.58), Indonesians (OR 4.15, 95% CI 1.69–10.19) and other non-Western immigrants (OR 3.57, 95% CI 1.62–7.85) were more likely to report hallucinations, whereas Western immigrants, Turkish males and Moroccan females did not differ from their Dutch counterparts. When adjusting for social adversity, the ORs for self-reported hallucinations among the non-Western immigrant groups showed considerable reductions of 28% to 52%.

In a general population sample, several non-Western immigrant groups reported hallucinations more often than Dutch natives, which is consistent with the higher incidence of psychotic disorders in most of these groups. The associations between ethnicity and hallucinations diminished after adjustment for social adversity, which supports the view that adverse social experiences contribute to the higher rate of psychosis among migrants.