Evidence suggests that cannabis may be a causal factor for development of schizophrenia. We aimed to investigate whether use of antipsychotic medication, benzodiazepines, and psychiatric service use differs among patients with schizophrenia depending on whether psychosis was precipitated by a diagnosis of cannabis use disorder (CUD).

We utilized the nationwide Danish registries to identify all individuals with an incident diagnosis of schizophrenia from 1995 to 2016. We also collected information on whether first CUD diagnosis preceded schizophrenia and thus defined a group of potentially cannabis-related schizophrenia. We compared the cannabis-related schizophrenia group both with all non-cannabis-related patients with schizophrenia and with non-cannabis-related patients with schizophrenia that were propensity-score matched to cases using a range of potentially confounding variables.

We included 35 714 people with incident schizophrenia, including 4116 (11.5%) that were cannabis-related. In the unmatched-comparison analyses, there were no clear differences over time in use of antipsychotics and benzodiazepines related to whether the diagnosis of schizophrenia was cannabis-related. After propensity-score matching, use of antipsychotics and benzodiazepines was significantly lower among cannabis-related cases of schizophrenia. In the unmatched comparison, the cannabis-related group had significantly more days admitted than the non-cannabis-related group. This was markedly attenuated after propensity-score matching.

Our findings indicate the importance of considering cannabis-related cases of schizophrenia as a potentially distinct disorder in terms of prognosis. It is unclear, however, if these differences are due to different biological types of schizophrenia being compared or if they rather indicate behavioral differences such as reduced adherence and treatment-seeking.

Case studies have linked SARS-CoV-2 infection to suicidal behaviour. However, conclusive evidence is lacking.

To examine whether a history of SARS-CoV-2 infection or SARS-CoV-2-related hospital admission was associated with self-harm in the general population and in high-risk groups.

A cohort design was applied to nationwide data on all people aged ≥15 years and living in Denmark between 27 February 2020 and 15 October 2021. Exposure was identified as having had a positive SARS-CoV-2 PCR test, and further assessed as SARS-CoV-2-related hospital admission. Rates of probable self-harm were examined using adjusted incidence rate ratios (aIRRs). The following subgroups were identified: (a) lower educational level, (b) chronic medical conditions, (c) disability pension, (d) mental disorders, (e) substance use disorders, and history of (f) homelessness and (g) imprisonment.

Among 4 412 248 included individuals, 260 663 (5.9%) had tested positive for SARS-CoV-2. Out of 5453 individuals presenting with self-harm, 131 (2.4%) had been infected. Individuals with a history of a positive SARS-CoV-2 test result had an aIRR for self-harm of 0.86 (95% CI 0.72–1.03) compared with those without. High rates were found after a SARS-CoV-2-related hospital admission (aIRR = 7.68; 95% CI 5.61–10.51) or a non-SARS-CoV-2-related admission (aIRR = 10.27; 95% CI 9.65–10.93) versus non-infected and not admitted. In sensitivity analyses with a more restrictive definition of self-harm, a positive PCR test was associated with lower rates of self-harm.

Individuals with a PCR-confirmed SARS-CoV-2 infection did not have higher rates of self-harm than those without. Hospital admission in general, rather than being SARS-CoV-2 positive. seemed to be linked to elevated rates of self-harm.

Discontinuation of antipsychotic medication may be linked to high risk of relapse, hospitalization and mortality. This study investigated the use and discontinuation of antipsychotics in individuals with first-episode schizophrenia in relation to cohabitation, living with children, employment, hospital admission and death.

Danish registers were used to establish a nationwide cohort of individuals ⩾18 years with schizophrenia included at the time of diagnosis in1995–2013. Exposure was antipsychotic medication calculated using defined daily dose and redeemed prescriptions year 2–5. Outcomes year 5–6 were analysed using binary logistic, negative binomial and Cox proportional hazard regression.

Among 21 351, 9.3% took antipsychotics continuously year 2–5, 38.6% took no antipsychotics, 3.4% sustained discontinuation and 48.7% discontinued and resumed treatment. At follow-up year 6, living with children or employment was significantly higher in individuals with sustained discontinuation (OR 1.98, 95% CI 1.53–2.56 and OR 2.60, 95% CI 1.91–3.54), non-sustained discontinuation (OR 1.25, 95% CI 1.05–1.48 and 2.04, 95% CI 1.64–2.53) and no antipsychotics (OR 2.00, 95% CI 1.69–2.38 and 5.64, 95% CI 4.56–6.97) compared to continuous users. Individuals with non-sustained discontinuation had more psychiatric hospital admissions (IRR 1.27, 95% CI 1.10–1.47) and longer admissions (IRR 1.68, 95% CI 1.30–2.16) year 5–6 compared to continuous users. Mortality during year 5–6 did not differ between groups.

Most individuals with first-episode schizophrenia discontinued or took no antipsychotics the first years after diagnosis and had better functional outcomes. Non-sustained discontinuers had more, and longer admissions compared to continuous users. However, associations found could be either cause or effect.

The mechanisms linking cardiovascular disease (CVD) and depression are still not established. We investigated the impact of mental vulnerability on the relationship between CVD and depression.

A total of 19,856 individuals from five cohorts of random samples of the background population in Copenhagen were followed from baseline (1983–2011) until 2017 in Danish registries. Additive hazard and Cox proportional hazard models were used to analyze the effects of confounding by mental vulnerability as well as interactions between mental vulnerability and CVD on the risk of depression.

During follow-up, 15.3% developed CVD, while 18.1% experienced depression. A strong positive association between CVD and depression (hazard ratio: 3.60 [95% confidence intervals (CI): 3.30; 3.92]) corresponding to 35.4 (95% CI: 31.7; 39.1) additional cases per 1,000 person-years was only slightly attenuated after adjustment for mental vulnerability in addition to other confounders. Synergistic interaction between CVD and mental vulnerability was identified in the additive hazard model. Due to interaction between CVD and mental vulnerability, CVD was associated with 50.9 more cases of depression per 1,000 person-years among individuals with high mental vulnerability compared with individuals with low mental vulnerability.

Mental vulnerability did not explain the strong relationship between CVD and depression. CVD was associated with additional cases of depression among individuals with higher mental vulnerability indicating that this group holds the greatest potential for intervention, for example, in rehabilitation settings.

Birth dimensions have been associated with increased risk of both, severe mental illness and type 2 diabetes in adulthood, however, any influence on their co-occurrence has never been examined. This cohort study examine whether birth weight/ponderal index explain or modify the later association between severe mental illness and risk of type 2 diabetes.

The Metropolit cohort included 10,863 Danish men born in 1953 with information from age at conscription (between1971-84) until February 15th, 2018. Severe mental illness was defined as the exposure and information was retrieved from the national Danish health registries. Information on type 2 diabetes diagnosis or oral antidiabetic prescriptions was also obtained, as they were the outcome of interest. Information on birth weight/ponderal index was available from birth certificates. Cox proportional hazards regression models were used to estimate the associations and interactions were tested.

After 47.1 years of follow-up, 848 (7.8%) and 1320 (12.2%) men developed a severe mental illness or diabetes, respectively. Men with severe mental illness presented higher risk of subsequent diabetes (HR = 1.92; 95%CI, 1.61–2.30). This association was stronger in severe mental ill men with low birth weight (HR = 3.58; 95%CI, 2.11–6.07), than in those normal birth weight (HR = 1.79; 95%CI, 1.45–2.20). This effect modification was most evident for men diagnosed with schizophrenia.

Birth information on birth weight/ponderal index could be of interest in diabetes screening on severe mental ill populations (especially in schizophrenia) since they might play a critical role in the increased risk of type 2 diabetes following severe mental illness.

Depression and cardiovascular diseases (CVDs) are common diseases and associated in a bidirectional manner.

To examine whether a bidirectional association between CVD and depression could be explained by shared risk factors, misclassification of disease measures or non-response.

A total of 10 population-based cohorts including 93 076 men and women (mean age 54.4 years, s.d. = 9.2) and an additional 10 510 men (mean age 51.2 years, s.d. = 0.3) were followed for subsequent depression, ischaemic heart disease (IHD) and stroke in the Danish National Patient Registry from health examinations between 1982 and 2015 and until end of follow-up in 2017–2018. Exposures were physicians’ diagnoses of IHD, stroke, depression or self-reported chest pain, depression, use of antidepressant medication and the Major Depression Inventory at the time of study entry in the Metropolit study. Associations were analysed using Cox proportional hazard regression with disease as time-dependent variables.

IHD and stroke were associated with subsequent depression (hazard ratio (HR) for IHD: 1.79, 95% CI 1.43–2.23 and HR for stroke: 2.62, 95% CI 2.09–3.29) and the associations were present in both men and women. Adjustment for the shared risk factors socioeconomic status, lifestyle, body mass index, statin use and serum lipids did not change the risk estimates. Furthermore, depression was associated with higher risk of subsequent IHD (HR = 1.63, 95% CI 1.36–1.95) and stroke (HR = 1.94, 95% CI 1.63–2.30). The associations were also present when the analyses were based on self-reported disease measures or restricted to include non-responders.

The bidirectional association between CVD and depression was not explained by shared risk factors, misclassification or non-response.

None.

Studies of the association between pre-deployment cognitive ability and post-deployment post-traumatic stress disorder (PTSD) have shown mixed results.

To study the inflence of pre-deployment cognitive ability on PTSD symptoms 6–8 months post-deployment in a large population while controlling for pre-deployment education and deployment-related variables.

Study linking prospective pre-deployment conscription board data with post-deployment self-reported data in 9695 Danish Army personnel deployed to different war zones in 1997–2013. The association between pre-deployment cognitive ability and post-deployment PTSD was investigated using repeated-measure logistic regression models. Two models with cognitive ability score as the main exposure variable were created (model 1 and model 2). Model 1 was only adjusted for pre-deployment variables, while model 2 was adjusted for both pre-deployment and deployment-related variables.

When including only variables recorded pre-deployment (cognitive ability score and educational level) and gender (model 1), all variables predicted post-deployment PTSD. When deployment-related variables were added (model 2), this was no longer the case for cognitive ability score. However, when educational level was removed from the model adjusted for deployment-related variables, the association between cognitive ability and post-deployment PTSD became significant.

Pre-deployment lower cognitive ability did not predict post-deployment PTSD independently of educational level after adjustment for deployment-related variables.

To validate intakes of protein, folic acid, retinol and n–3 fatty acids estimated from a food-frequency questionnaire in week 25 of pregnancy (FFQ-25).

Validation was done against a 7-day weighed food diary (FD) and biomarkers of the nutrients in gestation week 32–38.

The FFQ-25 to be validated was used in the Danish National Birth Cohort comprising 101 042 pregnant Danish women, of whom 88 participated in the present validation study.

Estimated intakes of protein, retinol and folic acid did not differ significantly between the two dietary methods, but intake of n–3 fatty acids was one third larger when estimated from the FFQ-25. The intakes estimated from the two dietary methods were all significantly correlated, ranging from 0.20 for retinol intake to 0.57 for folic acid intake. Sensitivities of being correctly classified into low and high quintiles were between 0.22 and 0.77, and specificities were between 0.62 and 0.89. Urinary protein content did not correlate significantly with protein estimated from the FFQ (r = 0.17, P > 0.05), but did with intake estimated from the FD (r = 0.56, P < 0.0001). Erythrocyte folate correlated significantly with the estimated total intake from the FFQ (r = 0.55, P < 0.0001) and the FD (r = 0.52, P < 0.0001). No correlations with plasma retinol were found. Erythrocyte eicosapentaenoic acid (C20:5n-3) correlated significantly with n–3 fatty acids intake estimated from both the FFQ-25 (r = 0.37, P < 0.001) and the FD (r = 0.62, P < 0.0001).

The FFQ-25 gives reasonable valid estimates of protein, retinol and folic acid intakes, but seems to overestimate intake of n–3 fatty acids.

Two British cohort studies have reported birth weight to be associated with self-reported depression in adulthood, even after adjustment for socio-economic factors.

To examine the relationship between birth dimensions and discharge from a psychiatric ward with a depression diagnosis in adulthood.

A cohort of 10 753 male singletons born in Copenhagen, Denmark in 1953 and for whom birth certificates had been traced in 1965 were followed from 1969 until 2002, with record linkage for date of first admission to a psychiatric ward that led to a discharge diagnosis of depression.

A total of 190 men, corresponding to 1.8% of the cohort, had a discharge diagnosis of depression. The Cox's regression analyses failed to show any association between birth dimensions (birth weight and ponderal index) and risk of psychiatric ward diagnosis of depression in adult life, before or after adjustment for social indicators at birth.

This study does not support the existence of a relation between birth dimensions and psychiatric ward admission for depression in adult men.