Social isolation, loneliness, and inflammation: A multi-cohort investigation in early and mid-adulthood.

Social isolation and loneliness have been associated with poor health and increased risk for mortality, and inflammation might explain this link. We used data from the Danish TRIAGE Study of acutely admitted medical patients (N = 6,144, mean age 60 years), and from two population-representative birth cohorts: the New Zealand Dunedin Longitudinal Study (N = 881, age 45) and the UK Environmental Risk (E-Risk) Longitudinal Twin Study (N = 1448, age 18), to investigate associations of social isolation with three markers of systemic inflammation: C-reactive protein (CRP), interleukin-6 (IL-6), and a newer inflammation marker, soluble urokinase plasminogen activator receptor (suPAR), which is thought to index systemic chronic inflammation. In the TRIAGE Study, socially isolated patients (those living alone) had significantly higher median levels of suPAR (but not CRP or IL-6) compared with patients not living by themselves. Social isolation prospectively measured in childhood was longitudinally associated with higher CRP, IL-6, and suPAR levels in adulthood (at age 45 in the Dunedin Study and age 18 in the E-Risk Study), but only suPAR remained associated after controlling for covariates. Dunedin Study participants who reported loneliness at age 38 or age 45 had elevated suPAR at age 45. In contrast, E-Risk Study participants reporting loneliness at age 18 did not show any elevated markers of inflammation. In conclusion, social isolation was robustly associated with increased inflammation in adulthood, both in medical patients and in the general population. It was associated in particular with systemic chronic inflammation, evident from the consistently stronger associations with suPAR than other inflammation biomarkers.

A magnetic resonance imaging-based morphometric and structural covariance network study of Brazilian adolescents stratified by depression risk

Objectives: To explore differences in regional cortical morphometric structure between adolescents at risk for depression or with current depression. Methods: We analyzed cross-sectional structural neuroimaging data from a sample of 150 Brazilian adolescents classified as low-risk (LR) (n=50) or high-risk (HR) for depression (n=50) or with current depression (n=50) through a vertex-based approach with measurements of cortical volume (CV), surface area (SA), and cortical thickness (CT). Differences between groups in subcortical volume and in the organization of networks of structural covariance were also explored. Results: No significant differences in brain structure between groups were observed in whole-brain vertex-wise CV, SA, or CT. Also, no significant differences in subcortical volume were observed between risk groups. In relation to the structural covariance network, there was an indication of an increase in the hippocampus betweenness centrality index in the HR group network compared to the LR and current depression group networks. However, this result was only statistically significant when applying false discovery rate correction for nodes within the affective network. Conclusion: In an adolescent sample recruited using an empirically based composite risk score, no major differences in brain structure were detected according to the risk and presence of depression.

Sex-specific inflammatory markers of risk and presence of depression in adolescents.

BACKGROUND: Associations between inflammatory markers and depression are reported among adults; however, less is known in adolescent depression in particular whether these associations are sex-specific. We aimed to identify inflammatory markers of increased risk and presence of depression in adolescence and their association with severity of depressive symptoms in the entire cohort and separately in boys and girls. METHODS: We measured serum cytokines using a Meso Scale Discovery electrochemiluminescence V-PLEX assay in a cohort of 150 adolescents stratified for risk/presence of depression. Risk group and sex-specific differences in inflammatory markers were assessed with 2-way mixed ANOVA, and sex-moderated associations between inflammatory markers and the severity of depressive symptoms were assessed with moderated multiple hierarchical regression analyses. RESULTS: We found a significant interaction between biological sex and the risk group, where boys showed higher interleukin (IL)-2 levels among the depressed group compared with the low-risk group. The severity of depressive symptoms was associated with elevated levels of IL-2 in boys, and of IL-6 in girls. There was a significant moderating effect of sex on the relationship between IL-2 and the severity of depressive symptoms but not for IL-6. LIMITATIONS: The cross-sectional design means that we cannot be certain about the direction of the associations. CONCLUSIONS: Our findings suggest sex-specific associations between inflammatory markers and the development of adolescent depression, where IL-2 may increase risk for depression and severity of depressive symptoms in boys, but not in girls. However, IL-6 may increase risk for more severe depressive symptoms in girls.

Identifying Depression Early in Adolescence: assessing the performance of a risk score for future onset of depression in an independent Brazilian sample

Objective: The Identifying Depression Early in Adolescence Risk Score (IDEA-RS) was recently developed in Brazil using data from the Pelotas 1993 Birth Cohort to estimate the individualized probability of developing depression in adolescence. This model includes 11 sociodemographic variables and has been assessed in longitudinal studies from four other countries. We aimed to test the performance of IDEA-RS in an independent, community-based, school-attending sample within the same country: the Brazilian High-Risk Cohort. Methods: Standard external validation, refitted, and case mix-corrected models were used to predict depression among 1442 youth followed from a mean age of 13.5 years at baseline to 17.7 years at follow-up, using probabilities calculated with IDEA-RS coefficients. Results: The area under the curve was 0.65 for standard external validation, 0.70 for the case mix-corrected model, and 0.69 for the refitted model, with discrimination consistently above chance for predicting depression in the new dataset. There was some degree of miscalibration, corrected by model refitting (calibration-in-the-large reduced from 0.77 to 0). Conclusion: IDEA-RS was able to parse individuals with higher or lower probability of developing depression beyond chance in an independent Brazilian sample. Further steps should include model improvements and additional studies in populations with high levels of subclinical symptoms to improve clinical decision making.

Physical activity and depressive symptoms among adolescents in a school-based sample

Objective: To explore associations between self-reported weekly physical activity and depressive symptomatology among adolescents in a school-based sample from Brazil. Methods: We surveyed 7,405 adolescents aged 14 to 16 years in 101 public schools in Porto Alegre, Brazil. We assessed physical activity using an adapted version of the Patient-Centered Assessment and Counseling for Exercise Plus Nutrition - Adolescent Physical Activity Measure (PACE+), and depressive symptoms using the Brazilian Portuguese version of the Patient Health Questionnaire - Adolescent Version. We compared the depressive symptom scores among adolescents with varying levels of physical activity. Results: Of the overall sample, 84.4% exercised less than the recommended frequency of 60 minutes/day, at least 5 days/week, of moderate to intense physical activity (PACE+ score ≥ 5). Adolescents whose physical activity levels fell below that threshold had higher median depression scores (8 [IQR = 10] vs. 7 [IQR = 9], W = 4060461, p < 0.001). A similar pattern was observed for depression scores in those with PACE+ < 1 (median of 10 [IQR = 11]) and ≥ 1 (7 [IQR = 9], W = 7457608, p < 0.001). Conclusion: In this large sample of Brazilian adolescents, those who exercised less frequently and vigorously than their peers reported more depressive symptoms.

Physical activity and depressive symptoms among adolescents in a school-based sample.

OBJECTIVE: To explore associations between self-reported weekly physical activity and depressive symptomatology among adolescents in a school-based sample from Brazil. METHODS: We surveyed 7,405 adolescents aged 14 to 16 years in 101 public schools in Porto Alegre, Brazil. We assessed physical activity using an adapted version of the Patient-Centered Assessment and Counseling for Exercise Plus Nutrition - Adolescent Physical Activity Measure (PACE+), and depressive symptoms using the Brazilian Portuguese version of the Patient Health Questionnaire - Adolescent Version. We compared the depressive symptom scores among adolescents with varying levels of physical activity. RESULTS: Of the overall sample, 84.4% exercised less than the recommended frequency of 60 minutes/day, at least 5 days/week, of moderate to intense physical activity (PACE+ score ≥ 5). Adolescents whose physical activity levels fell below that threshold had higher median depression scores (8 [IQR = 10] vs. 7 [IQR = 9], W = 4060461, p < 0.001). A similar pattern was observed for depression scores in those with PACE+ < 1 (median of 10 [IQR = 11]) and ≥ 1 (7 [IQR = 9], W = 7457608, p < 0.001). CONCLUSION: In this large sample of Brazilian adolescents, those who exercised less frequently and vigorously than their peers reported more depressive symptoms.

Longitudinal associations between adolescents' individualised risk for depression and inflammation in a UK cohort study.

Inflammation is associated with poor physical and mental health including major depressive disorder (MDD). Moreover, there is evidence that childhood adversity - a risk factor for MDD - becomes biologically embedded via elevated inflammation. However, the risk of developing MDD arises from multiple sources and yet there has been little investigation of the links between individuals' constellation of MDD risk and subsequent inflammation. We therefore examined associations between individual risk for MDD calculated in early adolescence and levels of inflammation six years later. We use data from the Environmental Risk (E-Risk) Longitudinal Twin Study, a nationally representative UK birth cohort of 2,232 children followed to age 18 with 93% retention. Participants' individual risk for developing future MDD was calculated at age 12 using a recently developed prediction model comprising multiple psychosocial factors. Plasma levels of three inflammation biomarkers were measured at age 18: C-reactive protein (CRP), interleukin-6 (IL-6), and a newer biomarker, soluble urokinase plasminogen activator receptor (suPAR), which is thought to reflect the level of systemic chronic inflammation. MDD risk scores calculated at age 12 were positively associated with levels of suPAR (but not CRP or IL-6) at age 18 after adjusting for key covariates (b = 1.70, 95% CI = 0.46 - 2.95, p = 0.007). Adolescents at high risk of MDD (risk scores ≥ 90th centile) had significantly higher mean levels of suPAR six years later than adolescents who had been identified as low risk (risk scores ≤ 10th centile) (b = 0.41, 95% CI = 0.18 - 0.64, p < 0.001). Findings support the notion that childhood psychosocial risk for MDD leads to increased levels of low-grade inflammation. If replicated in studies with repeated assessments of inflammation biomarkers throughout childhood and adolescence, these findings would support targeted interventions to reduce inflammation, as measured by suPAR, for adolescents at high risk of MDD to potentially prevent development of depression and physical health problems related to chronic inflammation.

Population vs Individual Prediction of Poor Health From Results of Adverse Childhood Experiences Screening.

Importance: Adverse childhood experiences (ACEs) are well-established risk factors for health problems in a population. However, it is not known whether screening for ACEs can accurately identify individuals who develop later health problems. Objective: To test the predictive accuracy of ACE screening for later health problems. Design, Setting, and Participants: This study comprised 2 birth cohorts: the Environmental Risk (E-Risk) Longitudinal Twin Study observed 2232 participants born during the period from 1994 to 1995 until they were aged 18 years (2012-2014); the Dunedin Multidisciplinary Health and Development Study observed 1037 participants born during the period from 1972 to 1973 until they were aged 45 years (2017-2019). Statistical analysis was performed from May 28, 2018, to July 29, 2020. Exposures: ACEs were measured prospectively in childhood through repeated interviews and observations in both cohorts. ACEs were also measured retrospectively in the Dunedin cohort through interviews at 38 years. Main Outcomes and Measures: Health outcomes were assessed at 18 years in E-Risk and at 45 years in the Dunedin cohort. Mental health problems were assessed through clinical interviews using the Diagnostic Interview Schedule. Physical health problems were assessed through interviews, anthropometric measurements, and blood collection. Results: Of 2232 E-Risk participants, 2009 (1051 girls [52%]) were included in the analysis. Of 1037 Dunedin cohort participants, 918 (460 boys [50%]) were included in the analysis. In E-Risk, children with higher ACE scores had greater risk of later health problems (any mental health problem: relative risk, 1.14 [95% CI, 1.10-1.18] per each additional ACE; any physical health problem: relative risk, 1.09 [95% CI, 1.07-1.12] per each additional ACE). ACE scores were associated with health problems independent of other information typically available to clinicians (ie, sex, socioeconomic disadvantage, and history of health problems). However, ACE scores had poor accuracy in predicting an individual's risk of later health problems (any mental health problem: area under the receiver operating characteristic curve, 0.58 [95% CI, 0.56-0.61]; any physical health problem: area under the receiver operating characteristic curve, 0.60 [95% CI, 0.58-0.63]; chance prediction: area under the receiver operating characteristic curve, 0.50). Findings were consistent in the Dunedin cohort using both prospective and retrospective ACE measures. Conclusions and Relevance: This study suggests that, although ACE scores can forecast mean group differences in health, they have poor accuracy in predicting an individual's risk of later health problems. Therefore, targeting interventions based on ACE screening is likely to be ineffective in preventing poor health outcomes.

Association of Neighborhood Disadvantage in Childhood With DNA Methylation in Young Adulthood.

Importance: DNA methylation has been proposed as an epigenetic mechanism by which the childhood neighborhood environment may have implications for the genome that compromise adult health. Objective: To ascertain whether childhood neighborhood socioeconomic disadvantage is associated with differences in DNA methylation by age 18 years. Design, Setting, and Participants: This longitudinal cohort study analyzed data from the Environmental Risk (E-Risk) Longitudinal Twin Study, a nationally representative birth cohort of children born between 1994 and 1995 in England and Wales and followed up from age 5 to 18 years. Data analysis was performed from March 15, 2019, to June 30, 2019. Exposures: High-resolution neighborhood data (indexing deprivation, dilapidation, disconnection, and dangerousness) collected across childhood. Main Outcomes and Measures: DNA methylation in whole blood was drawn at age 18 years. Associations between neighborhood socioeconomic disadvantage and methylation were tested using 3 prespecified approaches: (1) testing probes annotated to candidate genes involved in biological responses to growing up in socioeconomically disadvantaged neighborhoods and investigated in previous epigenetic research (stress reactivity-related and inflammation-related genes), (2) polyepigenetic scores indexing differential methylation in phenotypes associated with growing up in disadvantaged neighborhoods (obesity, inflammation, and smoking), and (3) a theory-free epigenome-wide association study. Results: A total of 1619 participants (806 female individuals [50%]) had complete neighborhood and DNA methylation data. Children raised in socioeconomically disadvantaged neighborhoods exhibited differential DNA methylation in genes involved in inflammation (ß = 0.12; 95% CI, 0.06-0.19; P < .001) and smoking (ß = 0.18; 95% CI, 0.11-0.25; P < .001) but not obesity (ß = 0.05; 95% CI, -0.01 to 0.11; P = .12). An epigenome-wide association study identified multiple CpG sites at an arraywide significance level of P < 1.16 × 10-7 in genes involved in the metabolism of hydrocarbons. Associations between neighborhood disadvantage and methylation were small but robust to family-level socioeconomic factors and to individual-level tobacco smoking. Conclusions and Relevance: Children raised in more socioeconomically disadvantaged neighborhoods appeared to enter young adulthood epigenetically distinct from their less disadvantaged peers. This finding suggests that epigenetic regulation may be a mechanism by which the childhood neighborhood environment alters adult health.

Association of Adverse Experiences and Exposure to Violence in Childhood and Adolescence With Inflammatory Burden in Young People.

Importance: Childhood stress exposure is associated with inflammation as measured by C-reactive protein (CRP) and interleukin 6 (IL-6). However, findings are inconsistent and effect sizes are small. The addition of soluble urokinase plasminogen activator receptor (suPAR), a new biomarker of chronic inflammation, may improve measurement of stress-related inflammatory burden. Objectives: To assess whether exposure to adverse experiences, stress, and violence is associated with an increase in suPAR levels in young people and to test the hypothesis that measuring suPAR in addition to CRP or IL-6 levels improves the assessment of the inflammatory burden associated with early-life stress. Design, Setting, and Participants: This cohort study included 1391 participants from a 1994 to 1995 birth cohort of twins from the nationally representative Environmental Risk Longitudinal Twin Study in the United Kingdom. Participants were followed up until 18 years of age (93% retention). Plasma samples were analyzed in July 2018, and statistical analysis was performed from October 1, 2018, to May 31, 2019. Exposures: Adverse childhood experiences and childhood and adolescent experience of stress and violence exposure. Main Outcomes and Measures: Plasma CRP, IL-6, and suPAR levels at 18 years of age. Results: Among 1391 young people (mean [SD] age, 18.4 [0.36] years; 733 [52.7%] female), those who had been exposed to stressful experiences had elevated suPAR levels by 18 years of age after controlling for sex, body mass index, and smoking: 0.03-ng/mL (95% CI, 0.01-0.05 ng/mL) increase in suPAR per each additional adverse childhood experience, 0.09-ng/mL (95% CI, 0.01-0.17 ng/mL) increase in suPAR per each additional severe childhood experience of stress or violence, and 0.04-ng/mL (95% CI, -0.02 to 0.10 ng/mL) increase in suPAR per each additional severe adolescent experience of stress or violence. Individuals exposed to multiple types of violence in both childhood and adolescence had 0.26-ng/mL (95% CI, 0.07-0.45 ng/mL) higher suPAR levels compared with children who did not experience stress or violence. These stress-exposed young people were significantly more likely to have elevated suPAR levels at 18 years of age even if they did not have elevated CRP or IL-6 levels. Measuring suPAR in addition to CRP or IL-6 increased the association between stress exposure and inflammatory burden. For example, after adjusting for CRP and IL-6 levels, each additional adverse childhood experience was associated with a 0.05-mL (95% CI, 0.03-0.07 ng/mL) increase in suPAR, each additional severe childhood experience of stress or violence was associated with a 0.14-ng/mL (95% CI, 0.06-0.22 ng/mL) increase in suPAR, and each additional severe adolescent experience of stress or violence was associated with a 0.10-ng/mL (95% CI, 0.04-0.16 ng/mL) increase in suPAR. Conclusions and Relevance: The results suggest that adult inflammation is associated with childhood exposure to stress. Adding information about suPAR to traditional biomarkers of inflammation may improve the measurement of inflammatory burden associated with exposure to stress and violence.

Association of Air Pollution Exposure With Psychotic Experiences During Adolescence.

Importance: Urbanicity is a well-established risk factor for clinical (eg, schizophrenia) and subclinical (eg, hearing voices and paranoia) expressions of psychosis. To our knowledge, no studies have examined the association of air pollution with adolescent psychotic experiences, despite air pollution being a major environmental problem in cities. Objectives: To examine the association between exposure to air pollution and adolescent psychotic experiences and test whether exposure mediates the association between urban residency and adolescent psychotic experiences. Design, Setting, and Participants: The Environmental-Risk Longitudinal Twin Study is a population-based cohort study of 2232 children born during the period from January 1, 1994, through December 4, 1995, in England and Wales and followed up from birth through 18 years of age. The cohort represents the geographic and socioeconomic composition of UK households. Of the original cohort, 2066 (92.6%) participated in assessments at 18 years of age, of whom 2063 (99.9%) provided data on psychotic experiences. Generation of the pollution data was completed on October 4, 2017, and data were analyzed from May 4 to November 21, 2018. Exposures: High-resolution annualized estimates of exposure to 4 air pollutants-nitrogen dioxide (NO2), nitrogen oxides (NOx), and particulate matter with aerodynamic diameters of less than 2.5 (PM2.5) and less than 10 µm (PM10)-were modeled for 2012 and linked to the home addresses of the sample plus 2 commonly visited locations when the participants were 18 years old. Main Outcomes and Measures: At 18 years of age, participants were privately interviewed regarding adolescent psychotic experiences. Urbanicity was estimated using 2011 census data. Results: Among the 2063 participants who provided data on psychotic experiences, sex was evenly distributed (52.5% female). Six hundred twenty-three participants (30.2%) had at least 1 psychotic experience from 12 to 18 years of age. Psychotic experiences were significantly more common among adolescents with the highest (top quartile) level of annual exposure to NO2 (odds ratio [OR], 1.71; 95% CI, 1.28-2.28), NOx (OR, 1.72; 95% CI, 1.30-2.29), and PM2.5 (OR, 1.45; 95% CI, 1.11-1.90). Together NO2 and NOx statistically explained 60% of the association between urbanicity and adolescent psychotic experiences. No evidence of confounding by family socioeconomic status, family psychiatric history, maternal psychosis, childhood psychotic symptoms, adolescent smoking and substance dependence, or neighborhood socioeconomic status, crime, and social conditions occurred. Conclusions and Relevance: In this study, air pollution exposure-particularly NO2 and NOx-was associated with increased odds of adolescent psychotic experiences, which partly explained the association between urban residency and adolescent psychotic experiences. Biological (eg, neuroinflammation) and psychosocial (eg, stress) mechanisms are plausible.

Interaction between childhood adversity and functional polymorphisms in the dopamine pathway on first-episode psychosis.

BACKGROUND: There is consistent evidence of a cumulative relationship between childhood adversity and psychosis, with number of adversities experienced increasing the probability of psychosis onset. It is possible that genetic factors moderate the association between childhood adversity and psychosis, potentially by influencing how an individual reacts biologically and/or psychologically following exposure to adversity, in such a way as to set them off on the path to psychosis. However, identifying the specific genetic variants involved and how they interact with childhood adversity remains challenging. We examined whether the association between cumulative exposure to childhood adversity and development of psychotic disorder was moderated by the COMT Val158Met, AKT1 rs2494732 or DRD2 rs1076560 polymorphisms, known to affect dopamine levels. METHODS: Participants were 285 first-presentation psychosis cases and 256 geographically-matched controls drawn from the Genetics and Psychosis (GAP) study. Childhood adversity was assessed using the Childhood Experience of Care and Abuse Questionnaire (CECA.Q) and blood- and cheek-derived genotype data were collected. RESULTS: Our findings revealed no main effect of COMT Val158Met, AKT1 rs2494732 and DRD2 rs1076560 polymorphisms on psychosis case status or reports of childhood adversity. Individuals reporting a history of multiple adversities were more likely to be psychosis patients than controls, regardless of their genetic risk. There was no evidence of candidate genotype by childhood adversity interactions in relation to psychosis onset. CONCLUSION: These findings did not provide evidence of a possible role of COMT Val158Met, AKT1 rs2494732 or DRD2 rs1076560 genotypes in modifying the association between childhood adversity and onset of psychosis.

Analysis of DNA Methylation in Young People: Limited Evidence for an Association Between Victimization Stress and Epigenetic Variation in Blood.

OBJECTIVE: DNA methylation has been proposed as an epigenetic mechanism by which early-life experiences become "embedded" in the genome and alter transcriptional processes to compromise health. The authors sought to investigate whether early-life victimization stress is associated with genome-wide DNA methylation. METHOD: The authors tested the hypothesis that victimization is associated with DNA methylation in the Environmental Risk (E-Risk) Longitudinal Study, a nationally representative 1994-1995 birth cohort of 2,232 twins born in England and Wales and assessed at ages 5, 7, 10, 12, and 18 years. Multiple forms of victimization were ascertained in childhood and adolescence (including physical, sexual, and emotional abuse; neglect; exposure to intimate-partner violence; bullying; cyber-victimization; and crime). RESULTS: Epigenome-wide analyses of polyvictimization across childhood and adolescence revealed few significant associations with DNA methylation in peripheral blood at age 18, but these analyses were confounded by tobacco smoking and/or did not survive co-twin control tests. Secondary analyses of specific forms of victimization revealed sparse associations with DNA methylation that did not replicate across different operationalizations of the same putative victimization experience. Hypothesis-driven analyses of six candidate genes in the stress response (NR3C1, FKBP5, BDNF, AVP, CRHR1, SLC6A4) did not reveal predicted associations with DNA methylation in probes annotated to these genes. CONCLUSIONS: Findings from this epidemiological analysis of the epigenetic effects of early-life stress do not support the hypothesis of robust changes in DNA methylation in victimized young people. We need to come to terms with the possibility that epigenetic epidemiology is not yet well matched to experimental, nonhuman models in uncovering the biological embedding of stress.

From Childhood Conduct Problems to Poor Functioning at Age 18 Years: Examining Explanations in a Longitudinal Cohort Study.

OBJECTIVE: Childhood conduct problems are associated with poor functioning in early adulthood. We tested a series of hypotheses to understand the mechanisms underlying this association. METHOD: We used data from the Environmental Risk (E-Risk) Longitudinal Twin Study, a birth cohort of 2,232 twins born in England and Wales in 1994 and 1995, followed up to age 18 years with 93% retention. Severe conduct problems in childhood were assessed at ages 5, 7, and 10 years using parent and teacher reports. Poor functioning at age 18 years, including cautions and convictions, daily cigarette smoking, heavy drinking, and psychosocial difficulties, was measured through interviews with participants and official crime record searches. RESULTS: Participants 18 years old with versus without a childhood history of severe conduct problems had greater rates of each poor functional outcome, and they were more likely to experience multiple poor outcomes. This association was partly accounted for by concurrent psychopathology in early adulthood, as well as by early familial risk factors, both genetic and environmental. Childhood conduct problems, however, continued to predict poor outcomes at age 18 years after accounting for these explanations. CONCLUSION: Children with severe conduct problems display poor functioning at age 18 years because of concurrent problems in early adulthood and familial risk factors originating in childhood. However, conduct problems also exert a lasting effect on young people's lives independent of these factors, pointing to early conduct problems as a target for early interventions aimed at preventing poor functional outcomes.

Interaction between cannabis consumption and childhood abuse in psychotic disorders: preliminary findings on the role of different patterns of cannabis use.

AIM: Several studies have suggested that lifetime cannabis consumption and childhood abuse synergistically contribute to the risk for psychotic disorders. This study aimed to extend existing findings regarding an additive interaction between childhood abuse and lifetime cannabis use by investigating the moderating role of type and frequency of cannabis use. METHODS: Up to 231 individuals presenting for the first time to mental health services with psychotic disorders and 214 unaffected population controls from South London, United Kingdom, were recruited as part of the Genetics and Psychosis study. Information about history of cannabis use was collected using the Cannabis Experiences Questionnaire. Childhood physical and sexual abuse was assessed using the Childhood Experience of Care and Abuse Questionnaire. RESULTS: Neither lifetime cannabis use nor reported exposure to childhood abuse was associated with psychotic disorder when the other environmental variable was taken into account. Although the combination of the two risk factors raised the odds for psychosis by nearly three times (adjusted OR = 2.94, 95% CI: 1.44-6.02, P = 0.003), no evidence of interaction was found (adjusted OR = 1.46, 95% CI: -0.54 to 3.46, P = 0.152). Furthermore, the association of high-potency cannabis and daily consumption with psychosis was at least partially independent of the effect of childhood abuse. CONCLUSIONS: The heavy use of high-potency cannabis increases the risk of psychosis but, in addition, smoking of traditional resin (hash) and less than daily cannabis use may increase the risk for psychosis when combined with exposure to severe childhood abuse.

Associations between adolescent cannabis use and neuropsychological decline: a longitudinal co-twin control study.

AIMS: This study tested whether adolescents who used cannabis or met criteria for cannabis dependence showed neuropsychological impairment prior to cannabis initiation and neuropsychological decline from before to after cannabis initiation. DESIGN: A longitudinal co-twin control study. SETTING AND PARTICIPANTS: Participants were 1989 twins from the Environmental Risk (E-Risk) Longitudinal Twin Study, a nationally representative birth cohort of twins born in England and Wales from 1994 to 1995. MEASUREMENTS: Frequency of cannabis use and cannabis dependence were assessed at age 18. Intelligence quotient (IQ) was obtained at ages 5, 12 and 18. Executive functions were assessed at age 18. FINDINGS: Compared with adolescents who did not use cannabis, adolescents who used cannabis had lower IQ in childhood prior to cannabis initiation and lower IQ at age 18, but there was little evidence that cannabis use was associated with IQ decline from ages 12-18. For example, adolescents with cannabis dependence had age 12 and age 18 IQ scores that were 5.61 (t = -3.11, P = 0.002) and 7.34 IQ points (t = -5.27, P < 0.001) lower than adolescents without cannabis dependence, but adolescents with cannabis dependence did not show greater IQ decline from age 12-18 (t = -1.27, P = 0.20). Moreover, adolescents who used cannabis had poorer executive functions at age 18 than adolescents who did not use cannabis, but these associations were generally not apparent within twin pairs. For example, twins who used cannabis more frequently than their co-twin performed similarly to their co-twin on five of six executive function tests (Ps > 0.10). The one exception was that twins who used cannabis more frequently than their co-twin performed worse on one working memory test (Spatial Span reversed; ß = -0.07, P = 0.036). CONCLUSIONS: Short-term cannabis use in adolescence does not appear to cause IQ decline or impair executive functions, even when cannabis use reaches the level of dependence. Family background factors explain why adolescent cannabis users perform worse on IQ and executive function tests.