To summarize insights generated during the preceding four conventions of the European Access Academy (EAA) regarding the interface of patient organizations and medical societies with the evolving European Union (EU) health technology assessment (HTA) process.

In 2022 and 2023 four EAA conventions were held on the EU HTA regulation, focusing on: (i) its relevance for beating cancer; (ii) stakeholder involvement; (iii) recommended preparatory steps to ensure its successful implementation; and (iv) the role of hematology and oncology as a pacemaker for the EU HTA process. Here we summarize insights generated at the four EAA conventions about the integration of patient and clinician insights in the evolving EU HTA process, including joint scientific consultations (JSC) and joint clinical assessments (JCA).

Throughout the conventions it became clear that the interface of patient associations and clinical societies with the EU HTA process is key for successful implementation of the regulation. All involved stakeholders rely on the principles of evidence-based medicine (EBM), including best internal and external evidence, patient values and expectations, and clinical experience. It was agreed that patient and clinician perspectives on the assessments are needed to balance the technical analysis of best external evidence. While patient input is rather well defined, when and how input from clinical societies is best incorporated during the process remains unclear.

As stipulated by the EBM triad, systematic involvement of patients and clinicians throughout both JSC and JCA is key to ensuring best outcomes for patients and society as a whole, in line with the objectives of the EU HTA regulation.

The association between cannabis and psychosis is established, but the role of underlying genetics is unclear. We used data from the EU-GEI case-control study and UK Biobank to examine the independent and combined effect of heavy cannabis use and schizophrenia polygenic risk score (PRS) on risk for psychosis.

Genome-wide association study summary statistics from the Psychiatric Genomics Consortium and the Genomic Psychiatry Cohort were used to calculate schizophrenia and cannabis use disorder (CUD) PRS for 1098 participants from the EU-GEI study and 143600 from the UK Biobank. Both datasets had information on cannabis use.

In both samples, schizophrenia PRS and cannabis use independently increased risk of psychosis. Schizophrenia PRS was not associated with patterns of cannabis use in the EU-GEI cases or controls or UK Biobank cases. It was associated with lifetime and daily cannabis use among UK Biobank participants without psychosis, but the effect was substantially reduced when CUD PRS was included in the model. In the EU-GEI sample, regular users of high-potency cannabis had the highest odds of being a case independently of schizophrenia PRS (OR daily use high-potency cannabis adjusted for PRS = 5.09, 95% CI 3.08–8.43, p = 3.21 × 10−10). We found no evidence of interaction between schizophrenia PRS and patterns of cannabis use.

Regular use of high-potency cannabis remains a strong predictor of psychotic disorder independently of schizophrenia PRS, which does not seem to be associated with heavy cannabis use. These are important findings at a time of increasing use and potency of cannabis worldwide.

Positive, negative and disorganised psychotic symptom dimensions are associated with clinical and developmental variables, but differing definitions complicate interpretation. Additionally, some variables have had little investigation.

To investigate associations of psychotic symptom dimensions with clinical and developmental variables, and familial aggregation of symptom dimensions, in multiple samples employing the same definitions.

We investigated associations between lifetime symptom dimensions and clinical and developmental variables in two twin and two general psychosis samples. Dimension symptom scores and most other variables were from the Operational Criteria Checklist. We used logistic regression in generalised linear mixed models for combined sample analysis (n = 875 probands). We also investigated correlations of dimensions within monozygotic (MZ) twin pairs concordant for psychosis (n = 96 pairs).

Higher symptom scores on all three dimensions were associated with poor premorbid social adjustment, never marrying/cohabiting and earlier age at onset, and with a chronic course, most strongly for the negative dimension. The positive dimension was also associated with Black and minority ethnicity and lifetime cannabis use; the negative dimension with male gender; and the disorganised dimension with gradual onset, lower premorbid IQ and substantial within twin-pair correlation. In secondary analysis, disorganised symptoms in MZ twin probands were associated with lower premorbid IQ in their co-twins.

These results confirm associations that dimensions share in common and strengthen the evidence for distinct associations of co-occurring positive symptoms with ethnic minority status, negative symptoms with male gender and disorganised symptoms with substantial familial influences, which may overlap with influences on premorbid IQ.