Mohammad R. Hayatbakhsh

Association between cannabis use and psychosis-related outcomes using sibling pair analysis in a cohort of young adults.

CONTEXT Prospective cohort studies have identified an association between cannabis use and later psychosis-related outcomes, but concerns remain about unmeasured confounding variables. The use of sibling pair analysis reduces the influence of unmeasured residual confounding. OBJECTIVE To explore the association between cannabis use and psychosis-related outcomes. DESIGN A sibling pair analysis nested within a prospective birth cohort. SETTING Births at a Brisbane, Australia, hospital. PARTICIPANTS Three thousand eight hundred one young adults born between 1981 and 1984 as part of the Mater-University Study of Pregnancy. MAIN OUTCOME MEASURES Cannabis use and 3 psychosis-related outcomes (nonaffective psychosis, hallucinations, and Peters et al Delusions Inventory score) were assessed at the 21-year follow-up. Associations between duration since first cannabis use and psychosis-related outcomes were examined using logistic regression adjusted for sex, age, parental mental illness, and hallucinations at the 14-year follow-up. Within 228 sibling pairs, the association between within-pair differences in duration since first cannabis use and Peters et al Delusions Inventory score was examined with general linear modeling. The potential impact of attrition was examined. RESULTS Duration since first cannabis use was associated with all 3 psychosis-related outcomes. For those with duration since first cannabis use of 6 or more years, there was a significantly increased risk of (1) nonaffective psychosis (adjusted odds ratio, 2.2; 95% confidence interval, 1.1-4.5), (2) being in the highest quartile of Peters et al Delusions Inventory score (adjusted odds ratio, 4.2; 95% confidence interval, 4.2-5.8), and (3) hallucinations (adjusted odds ratio, 2.8; 95% confidence interval, 1.9-4.1). Within sibling pairs, duration since first cannabis use and higher scores on the Peters et al Delusions Inventory remained significantly associated. CONCLUSIONS Early cannabis use is associated with psychosis-related outcomes in young adults. The use of sibling pairs reduces the likelihood that unmeasured confounding explains these findings. This study provides further support for the hypothesis that early cannabis use is a risk-modifying factor for psychosis-related outcomes in young adults.

Cannabis use and educational achievement: Findings from three Australasian cohort studies

BACKGROUND The associations between age of onset of cannabis use and educational achievement were examined using data from three Australasian cohort studies involving over 6000 participants. The research aims were to compare findings across studies and obtain pooled estimates of association using meta-analytic methods. METHODS Data on age of onset of cannabis use (<15, 15-17, never before age 18) and three educational outcomes (high school completion, university enrolment, degree attainment) were common to all studies. Each study also assessed a broad range of confounding factors. RESULTS There were significant (p<.001) associations between age of onset of cannabis use and all outcomes such that rates of attainment were highest for those who had not used cannabis by age 18 and lowest for those who first used cannabis before age 15. These findings were evident for each study and for the pooled data, and persisted after control for confounding. There was no consistent trend for cannabis use to have greater effect on the academic achievement of males but there was a significant gender by age of onset interaction for university enrolment. This interaction suggested that cannabis use by males had a greater detrimental effect on university participation than for females. Pooled estimates suggested that early use of cannabis may contribute up to 17% of the rate of failure to obtain the educational milestones of high school completion, university enrolment and degree attainment. CONCLUSIONS Findings suggest the presence of a robust association between age of onset of cannabis use and subsequent educational achievement.

Family Poverty Over the Early Life Course and Recurrent Adolescent and Young Adult Anxiety and Depression: A Longitudinal Study

OBJECTIVES We determined whether exposure to family poverty over a childs early life course predicts adolescent and young adult anxiety and depression. METHODS We used a birth cohort study of a sample of women in Brisbane, Australia, who were recruited in early pregnancy and whose children were followed up on at ages 14 and 21 years. Some 2609 mothers and adolescents provided usable data at the 14- and 21-year follow-ups. RESULTS After adjustment for poverty at other phases, poverty at the 14-year follow-up was the strongest predictor of adolescent and young adult anxiety and depression. The more frequently the child was exposed to poverty, the greater was the risk of that individual being anxious and depressed at both the 14- and 21-year follow-ups. CONCLUSIONS Family poverty predicts higher rates of adolescent and young adult anxiety and depression. Increased frequency of child exposure to poverty is a consistent predictor of adolescent and young adult anxiety and depression. Repeated experiences of poverty over a childs early life course are associated with increased levels of poor mental health.

Maternal smoking during and after pregnancy and lung function in early adulthood: a prospective study

Background and aims: There is a paucity of evidence about whether exposure to antenatal smoking impacts on offspring’s lung function in early adulthood. This study aimed to examine whether (1) in utero exposure to maternal smoking is related to poorer respiratory functioning in early adulthood; (2) the impact of prenatal smoking is independent of postnatal maternal smoking; and (3) the link between prenatal smoking and a young adult’s lung function is explained by the child’s birth weight, smoking or history of asthma. Methods: Data were from a 21-year follow-up of mothers and their children recruited into the Mater–University of Queensland Study of Pregnancy, a longitudinal prebirth cohort. The study is based on 2409 young adults (1185 males and 1224 females) who had prospective data available on respiratory function at 21 years and maternal smoking during and after pregnancy. A Spirobank G spirometer system was used to measure forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and forced expiratory flow between 25% and 75% of FVC (FEF25–75). Results: In utero exposure to maternal smoking was associated with a reduction in FEV1 and FEF25–75 in males (regression coefficient, −0.16; 95% CI, −0.30 to −0.02), after accounting for maternal smoking after pregnancy. At least part of the effect of in utero smoking on young adults’ lung function was explained by the child’s birth weight and subsequent asthma. Conclusions: Adverse effects of antenatal smoking on development of airway growth may persist into early adulthood. Gender differences noted in this longitudinal cohort need to be explored further.

Early overweight and pubertal maturation-pathways of association with young adults' overweight : a longitudinal study

Objective:Objectives of this study were to examine the prospective association of childhood body mass index (BMI) and overweight and pubertal stages with BMI and overweight in early adulthood independent of each other.Design:A population-based prospective birth cohort.Subjects:We used a population-based prospective birth cohort of 2897 (52% men) young adults who were born during 1981–1983 in Brisbane, Australia, and for whom we had puberty stages using Tanner scale at 14 years and measured BMI at 5 years of age.Main outcome measures:Pubertal stages at adolescent and BMI and its categories at 21 years.Results:We found that increasing BMI and overweight at 5 years of age predict the advanced stages of puberty. An advanced stage of puberty predicts young adults’ BMI and overweight status at 21 years. When taking both childhood BMI and pubertal status into consideration, we found that being overweight at 5 years substantively increases BMI at 21 years, regardless of the stage of puberty reported at 14 years. We also found that subjects with normal BMI at 5 years but with higher stages of puberty at 14 years had threefolds greater risk to be overweight at 21 years compared with their counterparts. All associations remained consistent after controlling for potential confounders.Conclusions:Although this study underscores the impact of both child overweight and pubertal development on young adults’ obesity, the mechanism that further explainsthe impact of puberty needs to be identified.

Early Childhood Predictors of Early Substance use and Substance use Disorders: Prospective Study

Objectives: The purpose of the present study was to examine the longitudinal association between early childhood factors and early initiation of use of substances and substance use disorders in a large prospective study. Method: Data were from the Mater Hospital University of Queensland Study of Pregnancy, a prospective birth cohort study in Brisbane, Australia. Use of nicotine, alcohol and cannabis and age of initiation of such use were reported at the 21 year follow up. DSM-IV diagnosis of nicotine, alcohol and cannabis use disorders was assessed at 21 years using a computerized version of the Composite International Diagnostic Interview (CIDI-Auto). Early childhood factors were measured between mothers pregnancy and child age 5 years. Results: Of the 3647 respondents with complete data, 15.4% had started to smoke cigarettes before 15 years. Another 17.4% and 12.2% reported having started to consume alcohol or use cannabis in early adolescence, respectively. Some 16.2%, 27.8% and 21.9% had ever had nicotine, alcohol or cannabis abuse or dependence (disorder) by 21 years, respectively. In multivariate models early initiation of use of substances, and substance use disorders were associated with disrupted families or drug-using parents, childhood problem behaviours, and poor parental monitoring and supervision in childhood. Conclusions: There are four independent factors in early or middle childhood that predict early initiation of use of substances and subsequent substance use disorders by early adulthood. There is a need to consider whether what is known about the risk factors that predict young age of substance use, and substance use disorders, may be incorporated into treatment and/or prevention initiatives.

Multiple Risk Factor Model Predicting Cannabis Use and Use Disorders: A Longitudinal Study

Background: Identification of factors associated with the initiation and continuation of cannabis use is important for any preventive work. Objectives: This study aimed to examine the early life course predictors of cannabis use and the development of cannabis use disorder in early adulthood. Methods: Data from Mater Hospital and University of Queensland Study of Pregnancy (MUSP), a population-based prospective birth cohort study. Participants were a cohort of 2,493 young adults who completed the life-time version of the Composite International Diagnostic Interview-computerized version (CIDI-Auto) at the 21-year follow-up, and for whom data were available from previous follow-ups. Ever use and age at first use of cannabis was assessed via self-report, and cannabis use disorder was measured based on Diagnostic and Statistical Manual version IV (DSM-IV) diagnostic criteria. Life course predictors were obtained between the childs birth and the 14-year follow-up. Results: Of 2,493 young adults, 51.4% reported having ever used cannabis, and 21.1% of young adults were classified as having ever had a cannabis use disorder. Childs gender, changes in maternal marital status, maternal smoking, child school performance, childhood sexual abuse, early adolescence smoking and alcohol consumption, and adolescent aggression/delinquency were strongly associated with young adult cannabis use and use disorder. Exposure to multiple risk factors was associated with greater risk of outcomes. Conclusions: There are a number of strong predictors of cannabis use identified in this study. They suggest that the social context within which children are reared has a major influence on cannabis use and use disorders.

The impact of episodic and chronic poverty on child cognitive development

OBJECTIVE To determine whether changes in family poverty between pregnancy, early childhood, and adolescence predict child cognitive development at 14 years of age. STUDY DESIGN We conducted a population-based prospective birth cohort study of 7223 mothers who gave birth to a live singleton baby, observed to 14 years of age. Family income was measured on 4 occasions from pregnancy to the 14-year follow-up. Child cognitive development was measured at the 14-year follow-up using the Ravens Standard Progressive Matrices and Wide Range Achievement Test. RESULTS Poverty experienced at any stage of the childs development is associated with reduced cognitive outcomes. Exposure to poverty for a longer duration (birth to 14 years) is more detrimental to cognitive outcomes than experiencing poverty at only 1 period. For each additional exposure to poverty, the Ravens Standard Progressive Matrices scores declined by 2.19 units and the Wide Range Achievement Test scores declined by 1.74 units. CONCLUSION Children experiencing family poverty at any developmental stage in their early life course have reduced levels of cognitive development, with the frequency that poverty is experienced predicting the extent of reduced cognitive scores.

Timing and Chronicity of Family Poverty and Development of Unhealthy Behaviors in Children: A Longitudinal Study

PURPOSE To examine the impact of the timing and duration of family experiences of poverty over the child/adolescent early life course on child aggressive/delinquent behavior and tobacco and alcohol consumption. METHODS Data were taken from a large scale population based birth cohort study with repeated follow-ups until 21 years after the birth. Poverty was measured during the pregnancy, 6 months, 5 years, and 14 years after the birth. Aggressive/delinquent behavior was measured at 14- and 21-year follow-ups. Tobacco and alcohol consumption were measured at the 21-year follow-up. RESULTS In multivariate analysis, family poverty experienced at the 14-year follow-up predicted persistent aggressive/delinquent behavior as well as smoking and higher levels of alcohol consumption at the 21-year follow-up. However, the strongest associations were for recurrent experiences of family poverty, with the group that experienced repeated poverty (3-4 times) being more than twice more likely to be aggressive/delinquent at both 14 and 21 years, and to drink more than one glass of alcohol per day at 21 years. CONCLUSIONS Repeated experiences of poverty in early childhood and adolescence are strongly associated with a number of negative health-related behavior outcomes. Experience of poverty in the early adolescence seems to be the most sensitive period for such exposure.

Adolescent problem behaviours predicting DSM-IV diagnoses of multiple substance use disorder: Findings of a prospective birth cohort study

BackgroundWhether there is an independent association between problem behaviours and substance use disorders (SUD) needs further investigation. This study examined prospective associations of adolescent psychopathology and problem behaviours with SUD in early adulthood, and whether these associations are confounded by other factors.MethodData were from a prospective study of 2,429 young Australian adults from birth to the age of 21 when data on SUD were collected. Adolescent psychopathology and behaviour were assessed at 14 years via the Youth Self Report instrument on eight sub-scales of emotional and behavioural problems.ResultsIn multivariate analyses, attention problems, delinquency, and aggression were associated with both single and multiple SUD in early adulthood, with delinquent behaviour being the strongest predictor (OR = 2.0, 95% CI 1.4–2.9 for one SUD and OR = 3.6, 95% CI 2.4–5.0 for multiple SUDs).ConclusionsProblem behaviours, in particular delinquency and aggression in early adolescence predict long-term SUD. The results suggest that substance use prevention programs should target adolescents with early symptoms of psychopathology and problem behaviour.