Some psychotic experiences in the general population show associations with higher schizophrenia and other mental health-related polygenic risk scores (PRSs), but studies have not usually included interviewer-rated positive, negative and disorganised dimensions, which show distinct associations in clinical samples.

To investigate associations of these psychotic experience dimensions primarily with schizophrenia PRS and, secondarily, with other relevant PRSs.

Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort participants were assessed for positive, negative and disorganised psychotic experience dimensions from interviews, and for self-rated negative symptoms, at 24 years of age. Regression models were used to investigate associations between psychotic experience dimensions and schizophrenia and other PRSs (2500+ participants for each analysis).

Against expectation, none of the positive, negative or disorganised dimensions was associated with schizophrenia PRS. In secondary analysis, self-rated negative symptoms were associated with higher depression (β = 0.10 [95% CI 0.06–0.15]), anxiety (β = 0.09 [95% CI 0.04–0.13]), neuroticism (β = 0.11 [95% CI 0.06–0.15]) and autism (β = 0.09 [95% CI 0.05–0.13]) PRSs (all P < 0.001); and first-rank delusions were nominally associated with higher schizophrenia PRS (odds ratio 7.35 [95% CI 2.10–25.77], P = 0.002), although these experiences/symptoms were rare.

Positive, negative and disorganised psychotic experiences are probably not strongly associated with polygenic liability to schizophrenia in this general population cohort of young adults. Self-rated negative symptoms may indicate social withdrawal/low motivation due to higher polygenic liability to affective disorders or autism, and first-rank delusions may indicate higher polygenic liability to schizophrenia, but these findings require independent confirmation.

Maternal smoking has known adverse effects on fetal development. However, research on the association between maternal smoking during pregnancy and offspring intellectual disability (ID) is limited, and whether any associations are due to a causal effect or residual confounding is unknown.

Cohort study of all Danish births between 1995 and 2012 (1 066 989 persons from 658 335 families after exclusions), with prospectively recorded data for cohort members, parents and siblings. We assessed the association between maternal smoking during pregnancy (18.6% exposed, collected during prenatal visits) and offspring ID (8051 cases, measured using ICD-10 diagnosis codes F70–F79) using logistic generalised estimating equation regression models. Models were adjusted for confounders including measures of socio-economic status and parental psychiatric diagnoses and were adjusted for family averaged exposure between full siblings. Adjustment for a family averaged exposure allows calculation of the within-family effect of smoking on child outcomes which is robust against confounders that are shared between siblings.

We found increased odds of ID among those exposed to maternal smoking in pregnancy after confounder adjustment (OR 1.35, 95% CI 1.28–1.42) which attenuated to a null effect following adjustment for family averaged exposure (OR 0.91, 95% CI 0.78–1.06).

Our findings are inconsistent with a causal effect of maternal smoking during pregnancy on offspring ID risk. By estimating a within-family effect, our results suggest that prior associations were the result of unmeasured genetic or environmental characteristics of families in which the mother smokes during pregnancy.

Epidemiological evidence suggests risk for psychosis varies with ethnicity in Western countries. However, there is little evidence to date on the cross-cultural validity of screening instruments used for such comparisons.

Combining two existing UK population-based cohorts, we examined risk for reporting psychotic symptoms across White British (n = 3467), White Irish (n = 851), Caribbean (n = 1899), Indian (n = 2590), Pakistani (n = 1956) and Bangladeshi groups (n = 1248). We assessed the psychometric properties of the Psychosis Screening Questionnaire (PSQ) with a multiple-group confirmatory factor analysis, assessing the equivalence of factor loadings, response thresholds and residual variances in an analysis of measurement non-invariance.

Compared with prevalence among British Whites (5.4%), the prevalence of self-reported psychotic symptoms was greater in the Caribbean group (12.7%, adjusted OR = 2.38 [95% CI 1.84–3.07]). Prevalence was also increased among Pakistani individuals (8.3%, adjusted OR = 1.36 [1.01–1.84]) although this difference was driven by a greater likelihood of reporting paranoid symptoms. PSQ items for thought interference, strange experience and hallucination were measured in equivalent ways across ethnic groups. However, our measurement models suggested that paranoid symptoms were measured less reliably among ethnic minorities than among British Whites and appeared to exaggerate latent differences between Pakistani and White British groups when measurement non-invariance was not accounted for.

Notwithstanding evidence for measurement non-invariance, the greater risk for reporting psychotic symptoms among Caribbean individuals is unlikely to be an artefact of measurement. Greater residual variance in the recording of paranoid symptoms among ethnic minority respondents warrants caution in using this item to investigate ethnic variation in psychosis risk.